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PubMed1992

Selective immunosuppression by administration of major histocompatibility complex (MHC) class II-binding peptides. I. Evidence for in vivo MHC blockade preventing T cell activation.

Draining lymph node cells (LNC) from mice immunized with hen egg white lysozyme (HEL) display at their surface antigen-MHC complexes able to stimulate, in the absence of any further antigen addition, HEL peptide-specific, class II-restricted T cell hybridomas. Chloroquine addition to these LNC cultures fails to inhibit antigen presentation, indicating that antigenic complexes of class II molecules and HEL peptides are formed in vivo. MHC class II restriction of antigen presentation by LNC from HEL-primed mice was verified by the use of anti-class II monoclonal antibodies. Coinjection of HEL and the I-Ak-binding peptide HEL 112-129 in mice of H-2k haplotype inhibits the ability of LNC to stimulate I-Ak-restricted, HEL 46-61-specific T cell hybridomas. Similar results are obtained in mice coinjected with the HEL peptides 46-61 and 112-129. Inhibition of T hybridoma activation can also be observed using as antigen-presenting cells irradiated, T cell-depleted LNC from mice coinjected with HEL 46-61 and HEL 112-129, ruling out the possible role of either specific or nonspecific suppressor T cells. Inhibition of T cell proliferation is associated with MHC-specific inhibition of antigen presentation and with occupancy by the competitor of class II binding sites, as measured by activation of peptide-specific T cell hybridomas. These results demonstrate that administration of MHC class II binding peptide competitors selectively inhibits antigen presentation to class II-restricted T cells, indicating competitive blockade of class II molecules in vivo.

Amino Acid Sequence↗

PubMed1992

Purification and characterization of carbohydrate-binding peptides from Lotus tetragonolobus and Ulex europeus seed lectins using affinity chromatography.

Carbohydrate-binding peptides of several anti-H(O) leguminous lectins were obtained from endoproteinase Asp-N or Lys-C digests of L-fucose-binding Lotus tetragonolobus lectin (LTA) and Ulex europeus lectin I (UEA-I) and from that of a di-N-acetylchitobiose-binding Ulex europeus lectin II (UEA-II) by affinity chromatography on columns of Fuc-Gel (for LTA and UEA-I) and on a column of a mixture of several oligomers of N-acetyl-D-glucosamine (GlcNAc) coupled to Sepharose 4B (GlcNAc oligomer-Sepharose 4B) (for UEA-II). These peptides were retained on the Fuc-Gel or GlcNAc oligomer-Sepharose 4B column and were presumed to have an affinity for the columns. The amino acid sequences of the retarded peptides were determined using a protein sequencer.

Amino Acid Sequence↗

PubMed2002

The thioesterase domain from a nonribosomal peptide synthetase as a cyclization catalyst for integrin binding peptides.

Nonribosomal peptide synthetases responsible for the production of macrocyclic compounds often use their C-terminal thioesterase (TE) domain for enzymatic cyclization of a linear precursor. The excised TE domain from the nonribosomal peptide synthetase responsible for the production of the cyclic decapeptide tyrocidine A, TycC TE, retains autonomous ability to catalyze head-to-tail macrocyclization of a linear peptide thioester with the native sequence of tyrocidine A and can additionally cyclize peptide analogs that incorporate limited alterations in the peptide sequence. Here we show that TycC TE can catalyze macrocyclization of peptide substrates that are dramatically different from the native tyrocidine linear precursor. Several peptide thioesters that retain a limited number of elements of the native peptide sequence are shown to be substrates for TycC TE. These peptides were designed to integrate an Arg-Gly-Asp sequence that confers potential activity in the inhibition of ligand binding by integrin receptors. Although enzymatic hydrolysis of the peptide thioester substrates is preferred over cyclization, TycC TE can be used on a preparative scale to generate both linear and cyclic peptide products for functional characterization. The products are shown to be inhibitors of ligand binding by integrin receptors, with cyclization and N(alpha)-methylation being important contributors to the nanomolar potency of the best inhibitors of fibrinogen binding to alpha IIb beta 3 integrin. This study provides evidence for TycC TE as a versatile macrocyclization catalyst and raises the prospect of using TE catalysis for the generation of diverse macrocyclic peptide libraries that can be probed for novel biological function.

Amino Acid Sequence↗

PubMed2001

The X-ray crystal structure and putative ligand-derived peptide binding properties of gamma-aminobutyric acid receptor type A receptor-associated protein.

The gamma-aminobutyric acid receptor type A (GABA(A)) receptor-associated protein (GABARAP) has been reported to mediate the interaction between the GABA(A) receptor and microtubules. We present the three-dimensional structure of GABARAP obtained by x-ray diffraction at 1.75 A resolution. The structure was determined by molecular replacement using the structure of the homologous protein GATE-16. NMR spectroscopy of isotope-labeled GABARAP showed the structure in solution to be compatible with the overall fold but showed evidence of conformation heterogeneity that is not apparent in the crystal structure. We assessed the binding of GABARAP to peptides derived from reported binding partner proteins, including the M3-M4 loop of the gamma2 subunit of the GABA(A) receptor and the acidic carboxyl-terminal tails of human alpha- and beta-tubulin. There is a small area of concentrated positive charge on one surface of GABARAP, which we found interacts weakly with all peptides tested, but we found no evidence for specific binding to the proposed physiological target peptides. These results are compatible with a more general role in membrane targeting and transportation for the GABARAP family of proteins.

Adaptor Proteins, Signal Transducing↗

PubMed1994

Assembly and peptide binding of major histocompatibility complex class II heterodimers in an in vitro translation system.

In vitro transcription/translation of HLA-DR1 cDNAs in the presence of microsomal membranes was used to study the association of major histocompatibility complex class II molecules with peptide and invariant chain (Ii) in the endoplasmic reticulum (ER). HLA-DR alpha and HLA-DR beta subunits assembled into SDS-unstable heterodimers in the absence of exogenous peptide. The inclusion of synthetic peptides during the alpha/beta assembly process promoted their conversion to SDS-resistant heterodimers. Addition of Ii RNA during the translation of HLA-DR alpha and HLA-DR beta RNAs resulted in the formation of alpha/beta/Ii complexes. Peptide binding by class II molecules was detected even when excess Ii was present during alpha/beta assembly. These findings indicate that peptides can bind alpha/beta heterodimers in the ER microenvironment and suggest that peptides derived from cytosolic proteins that are presented by class II molecules at the cell surface may have bound to HLA-DR in the ER.

Amino Acid Sequence↗

PubMed2006

A resistin binding peptide selected by phage display inhibits 3T3-L1 preadipocyte differentiation.

BACKGROUND: Resistin, a newly discovered cysteine-rich hormone secreted mainly by adipose tissues, has been proposed to form a biochemical link between obesity and type 2 diabetes. However, the resistin receptor has not yet been identified. This study aimed to identify resistin binding proteins/receptor. METHODS: Three cDNA fragments with the same 11 bp 5' sequence were found by screening a cDNA phage display library of rat multiple tissues. As the reading frames of the same 11 bp 5' sequence were interrupted by a TGA stop codon, plaque lift assay was consequently used to prove the readthrough phenomenon. The stop codon in the same 11 bp 5' sequence was replaced by tryptophan, and the binding activity of the coded peptide [AWIL, which was designated as resistin binding peptide (RBP)] with resistin was identified by the confocal microscopy technique and the affinity chromatography experiment. pDual GC-resistin and pDual GC-resistin binding peptide were co-transfected into 3T3-L1 cells to confirm the function of resistin binding peptide. RESULTS: Three cDNA fragments with the same 11 bp 5' sequence were found. The TGA stop codon in reading frames of the same 11 bp 5' sequence was proved to be readthroughed. The binding activity of RBP with resistin was consequently identified. The expression of the resistin binding peptide in 3T3-L1 preadipocytes expressing pDual GC-resistin significantly inhibited the adipogenic differentiation. CONCLUSION: RBP could effectively rescue the promoted differentiation of resistin overexpressed 3T3-L1 preadipocyte.

3T3-L1 Cells↗

PubMed2001

Induction of tumor specific cytotoxic T lymphocytes in prostate cancer using prostatic acid phosphatase derived HLA-A2402 binding peptide.

PURPOSE: Human prostatic acid phosphatase is a prostate specific differentiation antigen. Prostatic acid phosphatase levels increase in the serum of patients with prostate cancer and its peptide from positions 299 to 307 (PAP 299-307) is recognized by HLA-A2 restricted cytotoxic T lymphocytes. We investigated whether HLA-A2402 binding prostatic acid phosphatase derived peptides induce HLA-A2402 restricted, tumor specific cytotoxic T lymphocytes from the peripheral blood mononuclear cells of patients with prostate cancer. MATERIALS AND METHODS: Peptide binding activity was measured with RMA-S-A*A2402 cell lines and flow cytometry. Cytotoxic T-lymphocyte activity of the peripheral blood mononuclear cells of patients with prostate cancer and healthy donors was measured by interferon-gamma and (51)creatinine release assays. Prostatic acid phosphatase expression in the tumor cell lines at the messenger RNA and protein levels was investigated by reverse transcriptase-polymerase chain reaction and immunohistochemical analysis, respectively. RESULTS: An HLA-A2402 binding, prostatic acid phosphatase derived peptide consisting of the prostatic acid phosphatase amino acid sequence from positions 213 to 221 (PAP 213-221, LYCESVHNF) showed the ability to induce HLA-A2402 restricted and tumor specific cytotoxic T lymphocytes, which are cytoxic to prostatic acid phosphatase positive tumor cells from the peripheral blood mononuclear cells of patients with prostate cancer. CONCLUSIONS: PAP 213-221 may be appropriate as a cancer vaccine for specific immunotherapy in patients with HLA-A2402 positive prostate cancer.

Acid Phosphatase↗

PubMed1995

Use of a constrain phage displayed-peptide library for the isolation of peptides binding to HIV-1 nucleocapsid protein (NCp7).

It has been shown that peptide libraries are powerful tools for the identification of peptides showing new binding specificity. This technology was applied to the isolation of peptides binding to HIV-1 nucleocapsid protein (NCp7). Three different prolin reach peptide sequences, interacting with NCp7, were isolated, from a constrained phage displayed-peptide library of 10(8) independent clones. The three peptide sequences, isolated from the peptide library, were shown to bind NCp7 in the region 30-52. Moreover, two of them share the PP-(D/E)R consensus sequence.

Amino Acid Sequence↗

PubMed1992

Identity of a membrane-bound vasoactive intestinal peptide-binding protein with calmodulin.

A vasoactive intestinal peptide (VIP)-binding protein purified from guinea pig lung membranes (p18) was digested with trypsin, and the amino acid sequence of the peptide fragments was determined. The sequence of six tryptic fragments of p18 was identical with subsequences present in mammalian calmodulin. Authentic porcine brain calmodulin and p18 co-migrated on an sodium dodecyl sulfate-electrophoresis gel and displayed identical chromatographic behavior on a reverse phase high performance liquid chromatography column. The VIP-binding properties of p18 and calmodulin were indistinguishable. Both proteins displayed saturable and apparent high affinity binding of VIP, evidenced by potent inhibition of complexation with [Tyr10-125I]VIP by unlabeled VIP (IC50 = 6.0-8.1 nM). Rat growth hormone releasing factor and a C terminally extended form of VIP ([Leu17]VIP-GKR) also displayed potent inhibition of the binding (IC50 = 6.4 and 4 nM, respectively). These neuropeptides are potential modulators of calmodulin function.

Amino Acid Sequence↗

PubMed1992

Peptide binding to lipid bilayers. Nonclassical hydrophobic effect and membrane-induced pK shifts.

The binding of the cyclic peptide (+)-D-Phe1-Cys2-Phe3-D-Trp4-(+)-Lys5-Thr6- Cys7-Thr(ol)8, a somatostatin analogue (SMS 201-995), and the potential-sensitive dye 2-(p-toluidinyl)naphthalene-6-sulfonate (TNS) to lipid membranes was investigated with high-sensitivity titration calorimetry. The binding enthalpy of the peptide was found to vary dramatically with the vesicle size. For highly curved vesicles with a diameter of d congruent to 30 nm, the binding reaction was enthalpy-driven with delta H congruent to -7.0 +/- 0.3 kcal/mol; for large vesicles with more tightly packed lipids, the binding reaction became endothermic with delta H congruent to +1.0 +/- 0.3 kcal/mol and was entropy-driven. In contrast, the free energy of binding was almost independent of the vesicle size. The thermodynamic analysis suggests that the observed enthalpy-entropy compensation of about 8 kcal/mol can be related to a change in the internal tension of the bilayer and is brought about by an entropy increase of the lipid matrix. The "entropy potential" of the membrane may have its molecular origin in the excitation of the hydrocarbon chains to a more disordered configuration and may play a more important role in membrane partition equilibria than the classical hydrophobic effect. The binding of the peptide to the membrane surface induced a pK shift of the peptide terminal amino group. Neutral membranes were found to destabilize the NH3+ group, leading to a decrease in pK; negatively charged membranes, generated an apparent increase in pK due to the increase in proton concentration near the membrane surface. No pK shifts were seen for TNS. Titration calorimetry combined with the Gouy-Chapman theory can be used to determine both the reaction enthalpy and the binding constant of the membrane-binding equilibrium.

Amino Acid Sequence↗

PubMed1998

[The association of HLA-B27 binding peptide and spondylarthropathies].

OBJECTIVE: To explore the association of spondylarthropathies HAL-B27 binding peptide. METHODS: B27 molecules expressed on the B27-T2 mutant cell line do not have peptides. Such empty B27 molecules were not recognized by peptide-dependent monoclonal antibody, B27.M2. Positive B27.M2 reactivity resulted when B27-T2 cells were incubated with peptide RRKAMFEDI derived from Chlamydia hsp60. THe importance of each residue in RRKAMFEDI was analysed by testing analogs in which each of the 9 residues in the peptide was consecutively substituted by 19 other amino acids. RESULTS: B27.M2 reactivity was the highest with arginine in second residue. The reactivities of residues other than arginine were less than 30% of the value with the parent peptide. CONCLUSION: The stringency for other residues was relatively low, indicating that immune recognition of B27-peptide complexes might have rather low stringency for peptide sequences. These peptide residues probably influenced antibody reactivity by inducing conformational changes.

HLA-B27 Antigen↗

PubMed2005

Structure of RNA aptamer complexed with an RNA-binding peptide of Tat with aid of residue-specific 13C, 15N labeling.

An RNA aptamer containing two binding sites of HIV Tat exhibits extremely high affinity to Tat. We have determined the structure of the aptamer complexed with an RNA-binding peptide of Tat. The analysis was made feasible by the use of several peptides in which a single arginine residue was specifically 13C, 15N-labeled. Residue specific labeling of the peptide enhanced the identification of intermolecular contacts, which are otherwise hard to identify due to spectral overlapping. The structure of the complex has revealed the origin of the high affinity of the aptamer to Tat.

Aptamers, Nucleotide↗

PubMed1989

A peptide binding protein having a role in antigen presentation is a member of the HSP70 heat shock family.

The T cell recognition of globular protein antigens requires the processing and presentation of the antigen by Ia-expressing APCs. Processing is believed to involve the uptake of antigen into an acidic compartment where proteolysis occurs. The resulting peptides containing the T cell antigenic determinant are associated with Ia and presented at the cell surface to the specific T cells. The mechanisms by which antigenic peptides become associated with Ia is not known. We previously described a peptide binding protein of 72/74 x 10(3) Mr (PBP72/74) that plays a role in antigen presentation as shown by the ability of an antiserum raised in rabbits to affinity-purified PBP72/74 to block presentation of cytochrome c to a cytochrome c-specific T cell hybrid. Here we show that PBP72/74 is recognized by mAbs specific for members of the HSP70 family of proteins. In Western blots PBP72/74 is bound by mAb 7.10, specific for an evolutionarily conserved epitope of HSP proteins and by mAb N27, specific for both the constitutively expressed and inducible 72/73 x 10(3) Mr HSP70 proteins. In addition, PBP72/74 shares a second common feature of the HSP proteins, that of binding to ATP. Indeed, ATP causes the release of PBP72/74 from binding to a peptide fragment of cytochrome c (Pc 81-104) and PBP72/74 can be eluted from ATP columns by Pc 81-104. Finally, a portion of PBP72/74 is shown to be present on B cell surfaces by immunofluorescence staining. Thus, it appears that characteristics of the heat shock proteins are shared by a protein playing a role in antigen presentation, suggesting some commonality in function.

Adenosine Triphosphate↗

PubMed1996

Invariant chain association with MHC class I: preference for HLA class I/beta 2-microglobulin heterodimers, specificity, and influence of the MHC peptide-binding groove.

MHC class I molecules require the assembly of heavy chain with beta2-microglobulin (beta 2m) and peptide in order to present Ag on the cell surface. Endoplasmic reticulum resident proteins associate with class I molecules and aid assembly. Free class I heavy chains associate with calnexin, which may facilitate association with beta 2m. Invariant chain (Ii) also associates with MHC class I molecules, but its role in class I assembly is not clear. We report here that Ii strongly associates with HLA class I/beta 2m heterodimers, but weakly with free class I heavy chains in HLA-B7-transfected T2 cells. Ii/HLA class I complexes persist stably within the endoplasmic reticulum/cis-Golgi compartment in peptide-processing deficient cells, but are much less prominent in normally processing cells. Furthermore, Ii differentially associates with variant HLA-B7 molecules that have peptide-binding groove mutations, and the degree of association correlates with HLA-B7 variant cell surface expression. Ii also shows HLA class I molecule specificity, associating to a greater degree with HLA-B7 than HLA-A2. Together these observations suggest that Ii stabilizes particular HLA class I/beta 2m heterodimers until peptide is loaded, and that this association may enhance class I cell surface expression.

Antigens, CD↗

PubMed1992

Immobilized metal ion affinity chromatography of synthetic peptides. Binding via the alpha-amino group.

Peptides synthesized by the solid-phase method can be efficiently purified in a single immobilized metal affinity chromatography step based on interaction with the alpha-amino group if, after coupling of each amino acid residue, unreacted amino groups are irreversibly blocked by acetylation and if no strongly metal-binding amino acids (His, Trp, Cys) are present in the sequence. A difference in basicity for alpha- and epsilon-amino functions of ca. 2 pH units is sufficiently large to allow selective binding of peptides to immobilized metal ions via the unprotonated alpha-amino group. The binding is pH-dependent: on Cu(2+)- and Ni(2+)-loaded supports most peptides are maximally retarded at pH values around 7.5 and 8.5, respectively. The decreased binding strength at lower pH values is due to protonation of the alpha-amino function, whereas the reduced affinity at higher pH is caused by metal ion transfer from the matrix to the peptide. The metal ion is captured in a multidentate chelate where, in addition to the alpha-amino group, up to three adjacent deprotonated amide nitrogens are coordinated to the metal. If the pH is raised further, additional metal ions may be bound in biuret-like structures. Immobilized Ni2+, owing to its higher selectivity and affinity, is the preferred chromatographic support if slightly basic conditions can be tolerated.

Amino Acid Sequence↗

PubMed1999

Selection of ganglioside GM1-binding peptides by using a phage library.

Ganglioside Gal beta1 --> 3GalNAc beta1 --> 4(NeuAc alpha2 --> 3) Gal beta1 --> 4Glc beta1 -->1'Cer (GM1)-binding peptides were obtained from a phage-displayed pentadecapeptide library by an affinity selection. The selection processes were in situ-monitored by a quartz-crystal microbalance method, on which a ganglioside GM1 monolayer was transferred. After five rounds of biopanning, the DNA sequencing of 18 selected phages showed that only three individual clones were selected. The peptide sequences of the random region were found to be DFRRLPGAFWQLRQP, GWWYKGRARPVSAVA and VWRLLAPPFSNRLLP. Binding constants of these phage clones to the GM1 monolayer were 10(10) M(-1). Three synthetic pentadecapeptides inhibited the binding of cholera toxin B subunit to the GM1 monolayer with an IC50 of 24, 13 and 1.0 microM, respectively. These peptides will be useful for searching functional roles of ganglioside GMI.

Amino Acid Sequence↗

PubMed1998

Substrate binding induces depolymerization of the C-terminal peptide binding domain of murine GRP78/BiP.

To investigate the role of each domain in BiP/GRP78 function, we have used a full-length recombinant BiP engineered to contain two enterokinase sites; one site is located after an N-terminal FLAG epitope, and a second site has been inserted at the junction between the N- and C-terminal domains (FLAG-BiP.ent). FLAG-BiP.ent oligomerizes into multiple species that interconvert with each other in a slow, concentration- and temperature-dependent equilibrium. Binding of ATP or AMP-PNP (adenosine 5'-(beta, gamma-imino)triphosphate), but not ADP, or of a peptidic substrate induces depolymerization of FLAG-BiP.ent and stabilization of monomeric species. Enterokinase cleavage of monomeric, nucleotide-free BiP.ent results in the physical dissociation of the 44-kDa N-terminal ATPase fragment (N44.ent) from the 30-kDa C-terminal substrate binding domain (C30.ent). Upon dissociation, the freed C-terminal substrate binding domain readily undergoes self-association while N44.ent remains monomeric. Enterokinase cleavage performed in the presence of a synthetic peptide prevents oligomerization of the freed C30.ent domain. Addition of ATP during enterokinase cleavage has no effect on C30.ent oligomerization. Our data clearly indicate that binding of a specific peptide onto the C-terminal domain, or ATP onto the N-terminal domain, induces internal conformational change(s) within the C30 domain that result(s) in BiP depolymerization.

Adenosine Triphosphate↗

PubMed1994

Calmodulin-binding peptides interfere with melanocyte-stimulating hormone receptor activity and stimulate adenosine 3',5'-monophosphate production in M2R mouse melanoma cells.

The MSH receptor belongs to a unique class of G-protein-coupled receptors, in which calcium ions control the binding affinity of MSH by a yet unknown mechanism. Possible involvement of a calcium-binding protein [e.g. calmodulin (CaM)] in the regulation of MSH receptor activity has been studied in the M2R mouse melanoma cell line. In this study, we tested the inhibitory effects of a group of calmodulin-binding peptides (CBPs) on MSH receptor activities in intact M2R cells and membrane preparations derived from them. We also report here on stimulatory effects of CBPs on cAMP production in M2R cells that could not be produced in other cell lines lacking MSH receptors. This group of CBPs includes synthetic peptides comprising the CaM-binding domains of Ca2+/CaM-dependent enzymes, cytotoxic venom peptides, and peptide hormones that have been reported to directly interact with CaM. The results show that CBPs, at micromolar concentrations, inhibit MSH binding and consequent adenylate cyclase stimulation in a specific and concentration-dependent manner, but have no effect on adenylate cyclase stimulation by prostaglandin E1. On the other hand, when MSH was omitted and forskolin (0.5-1 microM) was added instead, CBPs had the opposite effect on cAMP production, stimulating it in M2R cells, but not in other cell types tested. Thus, these peptides can be considered as antagonists of MSH receptor and partial agonists of M2R adenylate cyclase. In contrast to MSH, the stimulatory effects of CBPs were unaffected by EGTA, suggesting a Ca(2+)-independent action of these peptides. Using phospholipid vesicles and M2R cells, we recently showed that CBP activity in M2R cells may include direct partition into the lipid bilayer of the cell membrane, permitting interaction with hydrophobic lipid-inserted domains of components of the signal transducing machinery. Based on these findings, we suggest that the mechanism of action of CBPs in the M2R cells includes two major components: 1) interaction with the cell surface membrane and penetration into the lipid milieu, and 2) interaction with exposed or lipid-embedded protein epitopes intrinsically associated with the MSH-receptor system, thereby affecting the MSH receptor cascade.

Animals↗