Biomedical subjects

G Jung

Publications and source records attributed to G Jung.

At least 19 recordsLinked to original sources

PubMed1997

C/EBP alpha and C/EBPbeta play similar roles in the transcription of the human Cu/Zn SOD gene.

Copper/zinc-containing superoxide dismutase (Cu/Zn SOD) is one of the essential enzymes that protects cells in aerobic conditions. To understand the mechanism of transcriptional regulation of the human Cu/Zn SOD gene, the proximal promoter region of Cu/Zn SOD has been investigated. In a previous study, it was found that transcription factors of the Sp1 and C/EBP family are associated with the expression of human Cu/Zn SOD [Seo et al. (1996). Gene, 178, 177-180]. Of the four known C/EBP activators, the effects of C/EBP alpha and C/EBPbeta on the transcription of Cu/Zn SOD were examined. Usually, one of the two C/EBP factors, C/EBP alpha or C/EBPbeta, exclusively stimulates the target gene, but, unexpectedly, C/EBP alpha and C/EBPbeta stimulated the expression of Cu/Zn SOD to a similar extent in our experiments. LIP, a dominant negative regulator of the C/EBP family, inhibited the transcriptional activation of Cu/Zn SOD stimulated by C/EBP alpha and C/EBPbeta. These results suggest that C/EBP alpha and C/EBPbeta can substitute each other and play similar roles on the transcription of Cu/Zn SOD.

CCAAT-Enhancer-Binding Proteins↗

PubMed1997

The active domain of the herpes simplex virus protein ICP47: a potent inhibitor of the transporter associated with antigen processing.

The herpes simplex virus type 1 (HSV-1) protein ICP47 binds specifically to the transporter associated with antigen processing (TAP), thereby blocking peptide-binding and translocation by TAP and subsequent loading of peptides onto MHC class I molecules in the endoplasmic reticulum. In consequence, HSV-infected cells are masked for immune recognition by cytotoxic T-lymphocytes. To investigate the molecular details of this, so far, unique transporter-inhibitor interaction, the active domain and critical amino acid residues were identified by using short overlapping fragments and systematic deletions of the viral inhibitor. A fragment of 32 amino acid residues, ICP47(3-34), was found to be the minimal region harboring an activity to inhibit peptide-binding to TAP comparable to the action of the full-length protein and therefore representing the active domain. Further N or C-terminal truncations cause an abrupt loss in activity. Within the identified active domain, various mutants and chimeras of ICP47 derived from HSV-1 and HSV-2 helped to identify amino acid residues critical for TAP inhibition. On the basis of these results, therapeutic drugs could be designed that are applicable in treatment of allograft rejection or in novel vaccination strategies against HSV, restoring the ability of the immune system to recognize HSV-infected cells.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed1997

Recognition principle of the TAP transporter disclosed by combinatorial peptide libraries.

Transport of peptides across the membrane of the endoplasmic reticulum for assembly with MHC class I molecules is an essential step in antigen presentation to cytotoxic T cells. This task is performed by the major histocompatibility complex-encoded transporter associated with antigen processing (TAP). Using a combinatorial approach we have analyzed the substrate specificity of human TAP at high resolution and in the absence of any given sequence context, revealing the contribution of each peptide residue in stabilizing binding to TAP. Human TAP was found to be highly selective with peptide affinities covering at least three orders of magnitude. Interestingly, the selectivity is not equally distributed over the substrate. Only the N-terminal three positions and the C-terminal residue are critical, whereas effects from other peptide positions are negligible. A major influence from the peptide backbone was uncovered by peptide scans and libraries containing D amino acids. Again, independent of peptide length, critical positions were clustered near the peptide termini. These approaches demonstrate that human TAP is selective, with residues determining the affinity located in distinct regions, and point to the role of the peptide backbone in binding to TAP. This binding mode of TAP has implications in an optimized repertoire selection and in a coevolution with the major histocompatibility complex/T cell receptor complex.

ATP-Binding Cassette Transporters↗

PubMed1997

CD30 induction and cytokine profiles in hepatitis C virus core-specific peripheral blood T lymphocytes.

Since an efficient control of virus infections may depend on the appropriate lymphokine profile, we studied cytokine responses and CD30 induction, a recently proposed surrogate marker of type 2 cells, in 10 healthy anti-hepatitis C virus (HCV)-seropositive blood donors without viremia (group A) and in 15 patients with hepatitis C (group B). Intracytoplasmic IFN-gamma, IL-2, IL-4, and IL-10 were determined by triple-color flow cytometry in the CD3+ and CD3+/CD30+ lymphocyte subsets after stimulation of PBMC with rHCV core protein and five core-derived peptides corresponding to the four immunodominant Th epitopes C.T1 to C.T4. In group A, more type 1 cytokines were induced by the rHCV core protein and all immunodominant core peptides (p < 0.05), whereas IL-10-producing T cells were found more frequently in group B. Induction of CD30+ T cells was found almost exclusively in group B (p < 0.01). The difference in cytokine responses was due to the CD3+/CD30- T cell subset and not the CD3+/CD30+ subset, which predominantly produced both IL-10 and IFN-gamma, but only small amounts of IL-2 and IL-4. We conclude that immunodominant HCV core peptides induce preferentially type 1 cytokines in healthy anti-HCV-positive blood donors and CD30 expression in patients with chronic hepatitis C. However, in both groups, CD30+ T lymphocytes produce an intermediate Th0-like cytokine profile. Thus, chronicity in HCV infection may reflect a lack of type 1 cytokine production.

Adult↗

PubMed1997

The three-dimensional solution structure of the lantibiotic murein-biosynthesis-inhibitor actagardine determined by NMR.

The three-dimensional solution structure of the lantibiotic actagardine was determined at high resolution by homonuclear and heteronuclear two-dimensional and three-dimensional NMR spectroscopy in [2H3]acetonitrile/H2O (7:3). 133 non-trivial distance and 22 torsional-angle constraints were derived from the NMR data. An ensemble of 15 low-energy structures was calculated by distance geometry followed by an iterative relaxation-matrix-refinement procedure. The rmsd of the backbone coordinates with respect to the average structure was 17 pm. The two distinct thioether ring systems 1-6 and 7-19 were even better defined, with backbone rmsd of 10 pm and 14 pm, respectively. Actagardine shows a rigid compact globular shape based on the constraining bridging pattern, which is composed of an N-terminal lanthionine ring from residues 1-6 and three intertwined C-terminal methyllanthionine rings comprising residues 7-12, 9-17 and 14-19. In addition, this C-terminal ring system is stabilised by a short antiparallel beta sheet. A feature of the actagardine structure is the presence of two putative binding pockets. A pocket is generated by the covalent constraints of the C-terminal thioether ring system. The rim of this pocket is built up by a loop structure comprising residues 12-19, whose backbone amide protons are all directed to the centre of the pocket. The second pocket is formed by an L-shaped orientation of the N-terminal and C-terminal thioether ring systems. The only two hydrophilic amino acid residues of actagardine, Glu11 and Ser2, are directed to this pocket. A region of high sequence similarity with the related lantibiotic mersacidin is located exactly at the position of the second pocket (residues 3-12). This suggests that the second pocket is responsible for the antibiotic mode of action of actagardine and mersacidin as inhibitors of the murein biosynthesis of gram-positive bacteria.

Amino Acid Sequence↗

PubMed1997

Isolation, structure elucidation, and synthesis of a macrophage stimulatory lipopeptide from Mycoplasma fermentans acting at picomolar concentration.

Macrophages are typically stimulated by components of microbial cell walls. Surprisingly, cell wall-less mycoplasmas can also very efficiently stimulate macrophages. We showed recently that mycoplasma-derived lipopeptides constitute the active principle. We have now isolated a clone of Mycoplasma fermentans expressing mainly one macrophage-stimulating lipopeptide. This lipopeptide was detergent-extracted and isolated by reversed-phase high-performance liquid chromotography, using nitric oxide release from C3H/HeJ mouse macrophages as bioassay for detection. In contrast to "conventional" bacterial lipoproteins, this lipopeptide had a free NH2 terminus. Amino acid composition, sequence, and the molecular weight of 2,163. 3 are consistent with the following structure: S-(2, 3-bisacyloxypropyl)cysteine-GNNDESNISFKEK with one mole C16:0, and a further mole of a mixture of C18:0 and C18:1 fatty acid per lipopeptide molecule. The sequence could not be found in either the protein identification resource nor the Swiss Prot data bank. We named this 2-kD lipopeptide, macrophage-activating lipopeptide-2 (MALP-2). Synthetic dipalmitoyl MALP-2 and mycoplasma-derived MALP-2 were compared with the bioassay. Both lipopeptides showed an identical dose dependency with a half-maximal response at 10(-11) M concentration. MALP-2 may be one of the most potent natural macrophage stimulators besides endotoxin.

Amino Acid Sequence↗

PubMed1997

Identification of naturally processed T cell epitopes from glutamic acid decarboxylase presented in the context of HLA-DR alleles by T lymphocytes of recent onset IDDM patients.

Glutamic acid decarboxylase (GAD) has been defined as a major target antigen in insulin-dependent diabetes mellitus (IDDM). To identify the molecular ligands triggering a T cell response to GAD, a panel of human GAD65-specific T lymphocyte lines was generated from peripheral blood of three recent onset IDDM patients. All lines derived from a patient expressing the high-risk-conferring HLA-DR*0301/ *0401 haplotypes recognized a single epitope localized between amino acid positions 270 and 283 of GAD65, a stretch that is located in close proximity to the homology region shared with Coxsackie virus P2-C protein. All lines with this specificity were restricted to the DRA, B1*0401 product of the DR4 haplotype. Analysis of the GAD-specific T cell response in a second patient homozygous for DR4 haplotypes demonstrated that the same DRA, B1*0401 allele selected T cells specific for a different determinant. The T cell response profile in a third patient showed that DR*1501/ *1601-encoding haplotypes could present at least three different epitopes to GAD65-specific T lymphocytes. One of these epitopes was presented by a DR allele associated with the resistance-conferring DRB1*1501 haplotype. GAD-specific T cell lines could not be isolated from HLA class II-matched normal individuals. Our data reveal that (a) the T cell response to GAD65 is quite heterogenous in recent onset IDDM patients; (b) HLA-DR, not DQ, seems to be the principal restriction element used by T cells present at the onset of the disease; and (c) T cells responding to epitopes containing identical sequences to Coxsackie virus P2-C protein were not detected.

Alleles↗

PubMed1997

Identification of high potency microbial and self ligands for a human autoreactive class II-restricted T cell clone.

CD4+ class II-restricted T cells specific for self antigens are thought to be involved in the pathogenesis of most human autoimmune diseases and molecular mimicry between foreign and self ligands has been implicated as a possible mechanism for their activation. In this report we introduce combinatorial peptide libraries as a powerful tool to identify cross-reactive ligands for these T cells. The antigen recognition of a CD4+ T cell clone (TCC) specific for myelin basic protein peptide (MBP) (86-96) was dissected by the response to a set of 220 11-mer peptide sublibraries. Based on the results obtained with the libraries for each position of the antigen, artificial peptides were found that induced proliferative responses at much lower concentrations than MBP(86-96). In addition stimulatory ligands derived from protein sequences of self and microbial proteins were identified, some of them even more potent agonists than MBP(86-96). These results indicate that: (a) for at least some autoreactive CD4+ T cells antigen recognition is highly degenerate; (b) the autoantigen used to establish the TCC represents only a suboptimal ligand for the TCC; (c) a completely random and unbiased approach such as combinatorial peptide libraries can decrypt the spectrum of stimulatory ligands for a T cell receptor (TCR).

Amino Acid Sequence↗

PubMed1997

RNase H activity of human hepatitis B virus polymerase expressed in Escherichia coli.

Human Hepatitis B Virus (HBV) replication is accomplished by its own polymerase. The HBV RNase H domain of HBV polymerase has been expressed in Escherichia coli and purified by affinity column chromatography. The MBP-RNase H fusion protein (43 kDa MBP plus 17 kDa HBV RNase H domain) was proved to be RNase H by in vitro activity assay, inhibitor studies, and mutagenesis. The HBV RNase H domain represented the optimal RNase H activity in the presence of either 8 mM MgCl2 or 16 mM MnCl2. In Tris-Cl buffer, the optimum pH for MBP-RNase H fusion protein is between 7.7 and 8.2. The MBP-RNase H fusion protein required 40 mM monovalent cation for its enzyme activity, whereas it showed lower activity at a salt concentration of more than 100 mM. Ribonucleoside Vanadyl complex (RAV) and 2'-deoxyadenosine 5'-monophosphate (dAMP) inhibited the RNase H activity. Moreover, the mutation of highly conserved amino acids in the HBV RNase H domain diminished the RNase H activity. These results clearly suggest that the RNase H activity is separable from viral HBV polymerase enzymatic activities.

Blotting, Western↗

PubMed1997

Effect of leader peptide mutations on biosynthesis of the lantibiotic Pep5.

Lantibiotics are lanthionine-containing antibiotic peptides which are synthesized from ribosomal prepeptides by post-translational modification. In order to elucidate the function of a conserved motif in the N-terminal leader sequence of lantibiotic prepeptides, three amino acids were exchanged in the leader peptide sequence of the lantibiotic Pep5. Exchanging Phe-19 for Ser and Glu-16 for Lys in the FDLEI-motif, reduced Pep5 production to 35 and 38% of the control whereas, after exchanging Asp-6 for Ser and Glu-16 for Lys in the FDLEI-motif, reduced Pep5 production to 35 and 38% of the control whereas, after exchanging ASp-6 for Lys, the production was decreased only to 82%. Proteolytic fragments of Pep5 or incorrectly modified Pep5 molecules, indicative of incorrect modifications, were not found in the culture supernatant. Thus, in contrast to the biosynthesis of the lantibiotic nisin, the FDLEI-motif is not essential for biosynthesis of Pep5 and has no influence on correct ring formation or processing, but seems to be important for optimal biosynthesis rates.

Anti-Bacterial Agents↗

PubMed1997

C/EBP alpha is a major activator for the transcription of rat Cu/Zn superoxide dismutase gene in liver cell.

The rat Cu/Zn superoxide dismutase (SOD1) is expressed in all tissues. Sequence analysis of the SOD1 promoter region showed that none of the cis-elements of hepatocyte-specific nuclear factors (HNF) were observed. The cis-element of C/EBP alpha in the proximal region of the SOD1 promoter and the high level of C/EBP alpha in the liver tissue led us to focus on the transcriptional regulation of the SOD1 gene by C/EBP alpha. Cotransfection assays with the plasmid expressing transcription factor C/EBP alpha showed that C/EBP alpha transactivated SOD1 gene by 27 fold. The marked transactivation and direct binding of C/EBP alpha to the SOD1 promoter were confirmed by deletion analyses and mobility shift assays. These results suggested that C/EBP alpha plays a major role in the tissue distribution of SOD1.

Animals↗

PubMed1997

Early antibody response against hypervariable region 1 is associated with acute self-limiting infections of hepatitis C virus.

Antibodies directed to hypervariable region 1 (HVR1) of hepatitis C virus (HCV) have recently been shown to neutralize the corresponding HCV isolate in vitro. We analyzed the appearance of antibodies directed to HVR1 during the course of infection in a large group of patients who have been infected by the same isolate of a HCV contaminated anti-D immunoglobulin (HCV-AD78). An enzyme-linked immunosorbent assay (ELISA) was established using a synthetic peptide to detect antibodies against the main HVR1 variant of HCV-AD78. 207 sera obtained at different time points post infection (p.i.) of 51 patients having either acute self-limiting (n = 28) or chronic infection (n = 23) were studied. Antibodies directed to HVR1 were found at least at one time point during the infection course in 15 of 28 patients (53%) having acute self-limiting infections and in 17 of 23 patients (74%) with chronic disease. The time of appearance of anti-HVR1 was significantly different between these two patient groups (P < .025) although appearance and titers of other HCV-specific antibodies were found to be similar at early time points p.i. In acute self-limiting infections 9 of 21 sera (43%) of respective patients with sera available within the first 6 months p.i. were anti-HVR1 positive. The highest prevalence of anti-HVR1 in this group of patients was within month 6 to 12 p.i. (64%). None of the sera available after 24 months p.i. had such antibodies. In contrast, only 2 of 15 sera (13%) of chronically infected patients with respective time points of sera were anti-HVR1 positive within the first 6 months p.i. and only 5 of 18 sera (28%) were positive within month 7 to 12 p.i. Seven patients with chronic HCV infections showed at least two consecutive anti-HVR1 negative early time points up to month 18 p.i. Prevalence of anti-HVR1 after 24 months p.i. was high (84%) in this group of patients and most of the patients maintained high levels of anti-HVR1 for up to 17 years p.i. Our findings suggest clearance of virus by respective neutralizing antibodies resulting in a self-limiting infection and may have implications for prognosis of the disease and also for any future vaccine development.

Adult↗

PubMed1997

High affinity presentation of an autoantigenic peptide in type I diabetes by an HLA class II protein encoded in a haplotype protecting from disease.

Polymorphism of the genes coding for the human histocompatibility leukocyte antigen class II DR and DQ molecules makes the single largest genetic contribution to the risk of developing insulin-dependent diabetes mellitus (IDDM) and can be associated with highly elevated as well as decreased disease frequency. The mechanism of IDDM risk modification by HLA polymorphism is likely to involve differential presentation of autoantigenic peptides by HLA class II proteins. We have generated T cell lines (TCL) with specificity for the IDDM autoantigen 65 kDa glutamic acid decarboxylase (GAD65) from lymphocytes of two patients carrying HLA class II alleles associated with distinct risk of IDDM (DRB1*0101/0401 and 1302/1501). For both patients, TCL generated at various time points all recognized single epitopes mapped as GAD 88-99 and 248-257, respectively. These epitopes are presented by the DRB1*0101 and DRB5*0101, HLA class II molecules associated with a moderately elevated risk of IDDM, or carried in a strongly protective haplotype, respectively. In an HLA/peptide binding assay, epitope GAD 248-257 was shown to possess high affinity for DRB5*0101. This epitope overlaps with a central GAD peptide binding to the high risk allele DQB1*0302 and containing a Coxsackie P2C-identical mimicry sequence, raising the possibility of competition of DRB5*0101 and DQB1*0302 for binding of a central GAD65 fragment.

Adult↗

PubMed1997

Two types of modified cardiac Na+ channels after cytosolic interventions at the alpha-subunit capable of removing Na+ inactivation.

Failure of inactivation is the typical response of voltage-gated Na+ channels to the cytosolic presence of proteolytic enzymes, protein reagents such as N-bromoacetamide (NBA) or iodate, and antibodies directed against the linker between domains III and IV of the alpha-subunit. The present patch clamp experiments with cardiac Na+ channels aimed to test the hypothesis that these interventions may provoke the occurrence of non-inactivating Na+ channels with distinct kinetic properties. A site-directed polyclonal antibody (anti-SLP2, target sequence 1481-1496 of the cardiac Na+ channel alpha-subunit) eliminated fast Na+ inactivation to induce burst activity which was accompanied by the occurrence of two open states. A deactivation process terminated channel activity during membrane depolarization proceeding with time constants of close to 40 ms (at -40 mV). NBA-modified and iodatemodified Na+ channels were kinetically indistinguishable from the anti-SLP2-modified type since they likewise deactivate and, thus, attain an only moderate Po of close to 20%. This is fundamentally different from the behaviour of enzymatically-modified Na+ channels: after cytosolic proteolysis with alpha-chymotrypsin, trypsin or pronase, mean Po during membrane depolarization amounted to approximately 40% because deactivation operated extremely slowly and less efficiently (time constants 100-200 ms at -40 mV, as a minimum) or was virtually non-operating. Invitro cleavage of the synthetic linker sequence 1481-1496 confirmed that this part of the alpha-subunit provides a substrate for these peptidases or reactants for NBA but cannot be chemically modified by iodate. This iodate resistance indicates that iodate-modified Na+ channels are based on a structural alteration of still another region which is also involved in Na+ inactivation, besides the linker between domains III and IV of the alpha-subunit. Endogenous peptidases such as calpain did not affect Na+ inactivation. This stresses the stochastic nature of a kinetic peculiarity of cardiac Na+ channels, mode-switching to a non-inactivating mode.

Acetamides↗

PubMed1997

Late results after resection of benign hepatic tumors: clinical and radiological findings.

The purpose of our work was to provide data on the recurrence of resected benign hepatic lesions and to evaluate the value of follow-up examinations in this group of patients. From August to October 1993, 75 patients who had been admitted for liver surgery for benign tumors between 1975 and 1993 were controlled by physical examinations, serological tests, US, and, in the case of equivocal US findings, by CT. The histological diagnoses of the operative specimen included hydatidosis in 43 patients, focal nodular hyperplasia (FNH) in 12 patients, liver cell adenoma in 8 patients, cavernous hemangioma in 8 patients, and congenital cyst in 4 patients. Hepatic scars were observed in 36 of the 75 patients. Four cases of intrahepatic recurrence and 1 case of intraperitoneal spread were observed in the 42 patients with recent hydatosis. Long-term postoperative controls (specific serological tests, US) are necessary in the management of patients with hydatid disease. Follow-up examinations are not indicated in asymptomatic patients who have been operated on for FNH, hemangioma, or congenital cysts.

Adult↗

PubMed1997

Electropolymerization of a phenol-modified peptide for use in receptor-ligand interactions studied by surface plasmon resonance.

The combination of surface plasmon resonance (SPR) with an electrochemical method for surface modification is presented. The SLP1 sequence of the sodium channel protein of rat cardiac muscle cells was N-terminally modified with an electropolymerizable group and immobilized on a gold-coated glass slide by oxidative polymerization. The resulting peptide-functionalized substrate was incubated with a polyclonal-specific anti-SLP1 serum. Growth of the peptide layer and the immunological reaction between ligand and receptor were detected on-line by SPR. The applicability of this approach for the rapid and selective analysis of receptor-ligand interactions is demonstrated.

Amino Acid Sequence↗

PubMed1997

Prospective controlled study of hydroxyzine and cetirizine in pregnancy.

BACKGROUND: Hydroxyzine has been used for many years for the treatment of allergic symptoms. Cetirizine, an active metabolite of hydroxyzine, has become very popular for the treatment of allergy symptoms because of its efficacy without the sedating effects of the parent compound. Little is known about the safety of hydroxyzine use during pregnancy, and there are no published reports on the effects of cetirizine on pregnancy outcome. OBJECTIVE: To determine whether hydroxyzine and cetirizine are associated with any increased risk of malformations in humans. METHODS: All pregnant women counseled by the Motherisk Program in Toronto on the use of hydroxyzine or cetirizine during their pregnancies were enrolled in a prospective, controlled, observational study. The control group consisted of pregnant women matched for age, smoking, and alcohol consumption who were counseled for non-teratogenic drug. RESULTS: One hundred twenty women were followed after exposure to either hydroxyzine or cetirizine during pregnancy. Of these, 53 were exposed to hydroxyzine during organogenesis and 39 to cetirizine. There were no significant differences found between the hydroxyzine or cetirizine groups and the control groups in the pregnancy outcome: rate of livebirths, spontaneous or therapeutic abortion, or stillbirth. There was also no difference in the rates of major or minor anomalies, mean birth weight, mode of delivery, gestational age, or presence of neonatal distress. CONCLUSIONS: The use of hydroxyzine and cetirizine does not appear to be associated with increased teratogenic risk.

Abortion, Spontaneous↗

PubMed1997

ATP-dependent ferric hydroxamate transport system in Escherichia coli: periplasmic FhuD interacts with a periplasmic and with a transmembrane/cytoplasmic region of the integral membrane protein FhuB, as revealed by competitive peptide mapping.

The Escherichia coli iron transport system via ferrichrome belongs to the group of ATP-dependent transporters that are widely distributed in prokaryotes and eukaryotes. Transport across the cytoplasmic membrane is mediated by three proteins: FhuD in the periplasm, FhuB in the cytoplasmic membrane and FhuC (ATPase) associated with the inside of the cytoplasmic membrane. Interaction of FhuD with FhuB was studied in vitro with biotinylated synthetic 10 residue and 20-24 residue peptides of FhuB by determining the activity of beta-galactosidase linked to the peptides via streptavidin. Peptides identical in sequence to only one of the four periplasmic loops (loop 2), predicted by a transmembrane model of FhuB, and peptides representing a transmembrane segment and part of the adjacent cytoplasmic loop 7 of FhuB bound to FhuD. Decapeptides were transferred into the periplasm of cells through a FhuA deletion derivative that forms permanently open channels three times as large as the porins in the outer membrane. FhuB peptides that bound to FhuD inhibited ferrichrome transport, while peptides that did not bind to FhuD did not affect transport. These data led us to propose that the periplasmic FhuD interacts with a transmembrane region and the cytoplasmic segment 7 of FhuB. The transmembrane region may be part of a pore through which a portion of FhuD inserts into the cytoplasmic membrane during transport. The cytoplasmic segment 7 of FhuB contains the conserved amino acid sequence EAA...G (in FhuB DTA ...G) found in ABC transporters, which is predicted to interact with the cytoplasmic FhuC ATPase. Triggering of ATP hydrolysis by substrate-loaded FhuD may occur by physical interaction between FhuD and FhuC, which bind close to each other on loop 7. Although FhuB consists of two homologous halves, FhuB(N) and FhuB(C), the sites identified for FhuD-mediated ferrichrome transport are asymmetrically arranged.

Adenosine Triphosphate↗