Biomedical subjects

F Lottspeich

Publications and source records attributed to F Lottspeich.

At least 127 records · Page 7Linked to original sources

PubMed1996

A new PrfA-regulated gene of Listeria monocytogenes encoding a small, secreted protein which belongs to the family of internalins.

A mutant of Listeria monocytogenes EGD was constructed that carries an extended deletion removing the entire PrfA-regulated gene cluster from plcA to plcB and a second deletion inactivating the inlA gene. Upon supplementation of this mutant with multiple gene copies of prfA, a protein of 30 kDa was detected in the supernatant of the mutant strain. The gene encoding this protein was obtained by direct and inverse polymerase chain reaction using oligonucleotide primers that were deduced from partial amino acid sequences of the purified 30 kDa protein. The amino acid sequence of the gene product revealed a protein of 297 amino acids that carried eight repeat units with high homology to those of the two known internalin proteins A and B. This secretory protein, termed internalin C, is much smaller than InlA or InlB and its complete sequence is related to the two known internalins. The gene InlC is transcribed into a monocistronic mRNA from a single promoter which shows a typical consensus sequence for PrfA-binding at the position -40. In contrast to the transcription of the InlAB operon, which is downregulated after shift of an L. monocytogenes EGD culture from brain-heart infusion into minimum essential medium (MEM), transcription of inlC is induced in MEM like most of the other known PrfA-regulated virulence genes. In addition, InlC is strongly transcribed in the cytoplasm of phagocytic J774 cells whereas inlA is poorly transcribed under these conditions, suggesting that internalin C may play a role in a late stage of L. monocytogenes infection rather than in the uptake of L. monocytogenes by non-professional phagocytic cells. An InlC deletion mutant shows reduced virulence when tested in an intravenous mouse model, but intracellular replication of the mutant in Caco-2 and J774 cells appears to be comparable with that of the wild-type strain.

Amino Acid Sequence↗

PubMed1996

Architecture of coatomer: molecular characterization of delta-COP and protein interactions within the complex.

Coatomer is a cytosolic protein complex that forms the coat of COP I-coated transport vesicles. In our attempt to analyze the physical and functional interactions between its seven subunits (coat proteins, [COPs] alpha-zeta), we engaged in a program to clone and characterize the individual coatomer subunits. We have now cloned, sequenced, and overexpressed bovine alpha-COP, the 135-kD subunit of coatomer as well as delta-COP, the 57-kD subunit and have identified a yeast homolog of delta-COP by cDNA sequence comparison and by NH2-terminal peptide sequencing. delta-COP shows homologies to subunits of the clathrin adaptor complexes AP1 and AP2. We show that in Golgi-enriched membrane fractions, the protein is predominantly found in COP I-coated transport vesicles and in the budding regions of the Golgi membranes. A knock-out of the delta-COP gene in yeast is lethal. Immunoprecipitation, as well as analysis exploiting the two-hybrid system in a complete COP screen, showed physical interactions between alpha- and epsilon-COPs and between beta- and delta-COPs. Moreover, the two-hybrid system indicates interactions between gamma- and zeta-COPs as well as between alpha- and beta' COPs. We propose that these interactions reflect in vivo associations of those subunits and thus play a functional role in the assembly of coatomer and/or serve to maintain the molecular architecture of the complex.

Amino Acid Sequence↗

PubMed1996

A major transmembrane protein of Golgi-derived COPI-coated vesicles involved in coatomer binding.

Formation of non-clathrin-coated vesicles requires the recruitment of several cytosolic factors to the Golgi membrane. To identify membrane proteins involved in this budding process, a highly abundant type I transmembrane protein (p23) was isolated from mammalian Golgi-derived COPI-coated vesicles, and its cDNA was cloned and sequenced. It belongs to the p24 family of proteins involved in the budding of transport vesicles (Stamnes, M.A., M.W. Craighead, M.H. Hoe, N. Lampen, S. Geromanos, P. Tempst, and J.E. Rothman. 1995. Proc. Natl. Acad. Sci. USA. 92:8011-8015). p23 consists of a large NH2-terminal luminal domain and a short COOH-terminal cytoplasmic tail (-LRRFFKAKKLIE-CO2-) that shows similarity, but not identity, with the sequence motif-KKXX-CO2-, known as a signal for retrieval of escaped ER-resident membrane proteins (Jackson, M.R., T. Nilsson, and P.A. Peterson. 1990. EMBO (Eur. Mol. Biol. Organ.) J. 9:3153-3162; Nilsson, T., M. Jackson, and P.A. Peterson. 1989. Cell. 58:707-718). The cytoplasmic tail of p23 binds to coatomer with similar efficiency as known KKXX motifs. However, the p23 tail differs from the KKXX motif in having an additional motif needed for binding of coatomer. p23 is localized to Golgi cisternae and, during vesicle formation, it concentrates into COPI-coated buds and vesicles. Biochemical analysis revealed that p23 is enriched in vesicles by a factor of approximately 20, as compared with the donor Golgi fraction, and is present in amounts stoichiometric to the small GTP-binding protein ADP-ribosylation factor (ARF) and coatomer. From these data we conclude that p23 represents a Golgi-specific receptor for coatomer involved in the formation of COPI-coated vesicles.

Amino Acid Sequence↗

PubMed1996

Different protein patterns derived from follicular fluid of mature and immature human follicles.

The purpose of our study was to compare the protein patterns originating from fluids of mature and immature human follicles in order to gain further insight into their biochemical composition. A total of 10 patients were stimulated for in-vitro fertilization (IVF) using different stimulation protocols. Follicular fluids were aspirated transvaginally and analysed microscopically for the presence of oocytes. Follicular fluids were stored at -18 degrees C. Samples of 500 microliters were processed for two-dimensional gel electrophoresis. Up to 60 proteins in various groups could be detected. Seven protein spots were selected for chemical analysis by cutting them out of the gels and subjecting them to internal amino acid sequencing procedures. Our results can be summarized as follows: (i) major differences were not detected between the protein patterns from the various mature follicles of a particular patient, nor were significant differences observed in the proteins derived from follicular fluids collected from the seven patients with mature follicles; (ii) considerable differences were observed in the protein patterns derived from fluids of immature compared with mature follicles. Fluid from the three patients with immature follicles contained many fewer proteins, some of which were expressed at low levels. We conclude that the observed variations in protein composition of follicles of different developmental age reflect their physiological condition and serve as biomedical markers for follicular maturity.

Amino Acid Sequence↗

PubMed1996

Analysis of a Thermotoga maritima DNA fragment encoding two similar thermostable cellulases, CelA and CelB, and characterization of the recombinant enzymes.

Recombinant Escherichia coli clones displaying thermostable beta-glucanase activity were isolated from two different gene libraries of the hyperthermophilic bacterium Thermotoga maritima MSB8 (DSM 3109), and the nucleotide sequence of a 1,4-beta-glucanase gene designated celA was determined. Amino-terminal sequencing of cellulase I previously detected in T. maritima cells indicated that the celA gene encodes this beta-glucanase, which is now designated CelA. CelA, which has a calculated molecular mass of 29,732 Da, was purified from a recombinant E. coli strain to apparent homogeneity as judged by SDS-PAGE with a 44% yield. The enzyme was most active against soluble substrates such as mixed-linkage beta-glucan and CM-cellulose. CelA displayed remarkable thermostability, which was enhanced in the presence of high concentrations of salt. Downstream of the celA gene we found a second open reading frame, celB, whose nucleotide sequence was 58% identical to celA. Experimental proof that celB also encodes a beta-glucanase was obtained by separation from celA and expression in E. coli under the control of an efficient host promoter. According to the deduced amino acid sequences, CelB, in contrast to CelA, contains a signal peptide at the amino terminus. CelB and CelA had similar substrate specificities and temperature optima, but differed in their pH optima. Also, the addition of salt had a less stabilizing effect on CelB than on CelA. Nine 30 bp direct repeats, each itself representing a sequence with imperfect dyad symmetry, were detected upstream of the celA-celB cellulase gene cluster.

Amino Acid Sequence↗

PubMed1996

HL-60 leukemia cells produce an autocatalytically truncated form of matrix metalloproteinase-9 with impaired sensitivity to inhibition by tissue inhibitors of metalloproteinases.

92-kDa type IV collagenase/gelatinase (matrix metalloproteinase-9; MMP-9; gelatinase B) expression and secretion has been shown to correlate with the invasive and metastatic potential of various malignant cells. MMP activity is tightly controlled by specific tissue inhibitors of metalloproteinases (TIMPs). We found the leukemic cell line HL-60 constitutively to release a 94-kDa gelatinase which we identified as MMP-9 shortened by nine amino acids at its N-terminal end. An additional gelatinolytic activity was present in small amounts and identified as a 63-kDa fragment of MMP-9 generated by autocatalytical processing. Both enzymes were identical regarding their N-terminus, indicating C-terminal truncation for the former. Incubation of cells with phorbol ester resulted in elevated amounts of both enzymes in conditioned media and in the secretion of TIMP-1. Both gelatinases were shown to be activated by trypsin and organomercurials and to possess similar activities towards various substrates. However, the 63-kDa enzyme differed from the 94-kDa enzyme in a significantly reduced inhibition by recombinant TIMP-1 and TIMP-2. Thus, the 63-kDa fragment of MMP-9 once activated may escape the regulatory influence of its specific inhibitors and may thereby promote matrix degradation during invasion of leukemic cells.

Amino Acid Sequence↗

PubMed1996

Affinity purification of cellulose-binding enzymes of Clostridium stercorarium.

Cellulose-affinity chromatography proved to be a fast and efficient purification procedure for exoenzymes of the thermophilic anaerobe Clostridium stercorarium, suitable for the preparation of large amounts of enzymes for technical applications. The cellulose-binding enzymes could be identified as the C. stercorarium; cellulolytic enzymes Avicelase I and Avicelase II characterized previously as endo-1,4-beta-glucanase and exo-1,4-beta-glucanase. A third protein was identified as xylanase A, the major endo-1,4-beta-xylanase of this organism.

Amino Acid Sequence↗

PubMed1995

Cloning, structural organization and regulation of expression of the Penicillium chrysogenum paf gene encoding an abundantly secreted protein with antifungal activity.

An abundantly secreted, highly basic 12-kDa protein (PAF) was purified from the culture medium of Penicillium chrysogenum (Pc). Based on the N-terminal amino acid (aa) sequence of the protein, an oligodeoxyribonucleotide probe was derived and used for amplification of the encoding cDNA by PCR. This cDNA fragment encodes a Cys-rich preproprotein of 92 aa which appears to be processed to a mature product of 55 aa. The deduced aa sequence of the preproprotein reveals 42.6% identity to an antifungal protein (AFP) of Aspergillus giganteus. Agar diffusion tests confirmed that the Pc protein exhibits antifungal activity. In order to investigate the promoter region and the structural organization of the paf gene, a genomic 6-kb fragment was isolated and partially sequenced. Comparison of the nucleotide sequence of the genomic fragment and the cDNA clone revealed the presence of a coding region of 279 bp which is interrupted by two introns of 76 and 68 bp in length. In the promoter region, a typical TATA box, a motif resembling the fungal carbon catabolite repression element, as well as several putative GATA factor binding motifs, were found. Northern blot analysis indicated that the regulation of paf expression occurs at the level of mRNA transcription and is under control of carbon catabolite and nitrogen metabolite repression regulatory circuits.

Amino Acid Sequence↗

PubMed1995

Transcription factors Stat3 and Stat5b are present in rat liver nuclei late in an acute phase response and bind interleukin-6 response elements.

Proteins binding at the interleukin-6 response element of the rat alpha 2 macroglobulin gene were purified by a combination of chromatographic procedures including binding site-specific DNA-affinity chromatography as the principal step. Three polypeptides of 92, 91, and 86 kDa were enriched approximately 6,300-fold from nuclei of rat livers excised 12 h after the induction of an experimental acute phase response. Amino acid sequence analysis identified the 86- and 91-kDa species as two forms of the transcription factor Stat3 and the 92-kDa species as the factor Stat5b. This identification was confirmed by gel mobility shift-supershift experiments using specific antisera for Stat3 and Stat5. Unexpectedly, activated Stat5 was also detected in the nuclei of untreated control rats. cDNA clones representing Stat3 and two isoforms of Stat5b were isolated from a cDNA library prepared with mRNA from rat livers excised at the peak of an experimental acute phase response. Full-length Stat5b, predicted from cDNA, consisted of 786 amino acids, while the variant Stat5b delta 40C lacked 41 amino acids at the COOH terminus. The amino acid sequence of rat Stat5b showed 26.7% overall identity with rat Stat3, 87.3% with sheep Stat5a, 92.5% with murine Stat5a, and 98.7% with murine Stat5b.

Acute-Phase Proteins↗

PubMed1995

Chlamyrhodopsin represents a new type of sensory photoreceptor.

In order to find optimal light conditions for photosynthetic growth, the green alga Chlamydomonas uses a visual system. An optical device, a rhodopsin photoreceptor and an electrical signal transduction chain that mediates between photoreceptor and flagella comprise this system. Here we present an improved strategy for the preparation of eyespot membranes. These membranes contain a retinal binding protein, which has been proposed to be the apoprotein of the phototaxis receptor. The retinal binding protein, which we named chlamyopsin, was purified and opsin-specific antibodies were raised. Using these antibodies, the opsin was localized in the eyespot region of whole cells during growth and cell division. The opsin cDNA was purified and sequenced. The sequence reveals that chlamyopsin is not a typical seven helix receptor. It shows some homology to invertebrate opsins but not to opsins from halobacteria. It contains many polar and charged residues and might function as a light-gated ion channel complex. It is likely that this lower plant rhodopsin diverged from animal opsins early in opsin evolution.

Algal Proteins↗

PubMed1995

Isolation and structural characterization of different isoforms of the hypusine-containing protein eIF-5A from HeLa cells.

Posttranslational modification of a specific lysine residue in eukaryotic initiation factor 5A (eIF-5A) is essential for cell viability and proliferation. The product of this modification is hypusine, an amino acid unique to eIF-5A. We have purified and characterized one major and three minor isoforms of human eIF-5A from HeLa cells. The main form, which accounts for approximately 95% of the total eIF-5A, carries hypusine at position 50 and is amino-terminally acetylated as determined by amino acid composition analysis and electrospray ionization mass spectrometry. Analytical gel filtration indicates that this protein variant possesses a native apparent molecular weight that lies between that expected for a monomeric and dimeric form. Nevertheless, several experiments confirm this protein to be monomeric. It is further shown that eIF-5A have well-defined secondary structure. Both the far-UV circular dichroism spectrum as well as secondary structure predictions using different algorithms suggest this protein to have predominantly beta-sheet structure. Two plausible models for the packing of the secondary structure elements are presented. In contrast to the main form, all three minor isoforms of eIF-5A are characterized by acetylation of the epsilon-amino group of lysine at position 47. The minor isoforms are distinguishable by their state of modification of the lysine residue at position 50. Whereas the main form occurs in both the cytoplasmic and the nuclear fraction of HeLa cells, the minor isoforms were not detectable in the preparation of the nuclear fraction. Therefore, acetylation of lysine at position 47 might play a controlling role in the distribution of the minor isoforms to the nucleus.

Amino Acid Sequence↗

PubMed1995

Stress-induced tyrosine phosphorylation of actin in Dictyostelium cells and localization of the phosphorylation site to tyrosine-53 adjacent to the DNase I binding loop.

Actin is known to be phosphorylated at tyrosine, serine, or threonine residues in various cells. In cells of Dictyostelium discoideum, a rise in the tyrosine phosphorylation of actin is observed in response to ATP depletion. An actin fraction rich in phosphotyrosine was obtained by chromatography on the weak anion exchanger Mono-P. Mass spectrometry and amino acid sequencing of protease cleavage products indicated that a single tyrosine residue was phosphorylated. Localization of this residue to position 53 of the actin sequence attributed the modification to a site that is critical for the capability of actin to polymerize. Induction of the tyrosine phosphorylation by heat shock and Cd2+ ions indicates that this modification of actin is implicated in the response of Dictyostelium cells to stress.

Actins↗

PubMed1995

Photoaffinity labeling of human lysosomal beta-hexosaminidase B. Identification of Glu-355 at the substrate binding site.

The carbene precursor 3-azi-1-[([6-3H]-2-acetamido-2-deoxy-1-beta-D-galactopyranosyl)thi o -butane (also designated [3H]-1-ATB-GalNAc) has been used as a photoaffinity label for human lysosomal beta-hexosaminidase B (Hex B, EC 3.2.1.52) purified to apparent homogeneity from postmortal liver. [3H]-1-ATB-GalNAc behaved as an active site-directed inhibitor, which bound covalently to Hex B upon photolysis at 350 nm and resulted in 15% inactivation of enzyme activity. Up to 75% of the inactivation of Hex B was prevented by including the competitive inhibitor 2-acetamido-2-deoxy-D-glucono-1,5-lactone in the photoaffinity experiment. Incubation of [3H]-1-ATB-GalNAc with the enzyme followed by irradiation and subsequent separation of the three polypeptides composing the beta-subunit led mainly to labeling of the beta a-polypeptide. Subsequent proteolysis of beta a with trypsin and separation of the resulting peptides by high pressure liquid chromatography yielded one prominently labeled peptide fraction. Edman degradation resulted in the sequence E339ISEVFPDQFIHLGGD-EVEFK359. However, no modified amino acid was detected, indicating that the photoaffinity label was presumably bound to the peptide by a labile ester linkage. This was proven when the radiolabel was almost completely released from the peptide by treatment with aqueous ammonium hydroxide. Simultaneously, Glu-355 was converted into Gln-355, which is located within a region of Hex B that shows considerable homology with the alpha-subunit of human hexosaminidase A and other hexosaminidases from various species.

Affinity Labels↗

PubMed1995

Clostridial neurotoxins compromise the stability of a low energy SNARE complex mediating NSF activation of synaptic vesicle fusion.

A 20S complex composed of the cytosolic fusion proteins NSF and SNAP and the synaptosomal SNAP receptors (SNAREs) synaptobrevin, syntaxin and SNAP-25 is essential for synaptic vesicle exocytosis. Formation of this complex is thought to be regulated by synaptotagmin, the putative calcium sensor of neurotransmitter release. Here we have examined how different inhibitors of neurotransmitter release, e.g. clostridial neurotoxins and a synaptotagmin peptide, affect the properties of the 20S complex. Cleavage of synaptobrevin and SNAP-25 by the neurotoxic clostridial proteases tetanus toxin and botulinum toxin A had no effect on assembly and disassembly of the 20S complex; however, the stability of its SDS-resistant SNARE core was compromised. This SDS-resistant low energy conformation of the SNAREs constitutes the physiological target of NSF, as indicated by its ATP-dependent disassembly in the presence of SNAP and NSF. Synaptotagmin peptides caused inhibition of in vitro binding of this protein to the SNAREs, a result that is inconsistent with synaptotagmin's proposed role as a regulator of SNAP binding. Our data can be reconciled by the idea that NSF and SNAP generate synaptotagmin-containing intermediates in synaptic vesicle fusion, which catalyse neurotransmitter release.

Adenosine Triphosphate↗

PubMed1995

Molecular biological analysis of a bidirectional hydrogenase from cyanobacteria.

An 8.9-kb segment with hydrogenase genes from the cyanobacterium Anabaena variabilis has been cloned and sequenced. The sequences show homology to the methyl-viologen-reducing hydrogenases from archaebacteria and, even more striking, to the NAD(+)-reducing enzymes from Alcaligenes eutrophus and Nocardia opaca as well as to the NADP(+)-dependent protein from Desulfovibrio fructosovorans. The cluster from A. variabilis contains genes coding for both the hydrogenase heterodimer (hoxH and hoxY) and for the diaphorase moiety (hoxU and hoxF) described for the A. eutrophus enzyme. In A. variabilis the gene cluster is split by two open reading frames (between hoxY and hoxH and between hoxU and hoxY, respectively), and a probably non-coding 0.9-kb segment in an unusual way. The hoxH partial sequence from Anabaena 7119 and Anacystis nidulans was amplified by PCR. Using the labeled segment from A. 7119 as probe, Southern analysis revealed homologous gene segments in the cyanobacteria A. 7119, Anabaena cylindrica, Anacystis nidulans and A. variabilis. The bidirectional hydrogenase from A. nidulans was purified and digests were sequenced. The amino acid sequences obtained showed partial identities to the amino acid sequences deduced from the DNA data of the 8.9-kb segment from A. variabilis. Therefore the 8.9-kb segment contains the genes coding for the bidirectional, reversible hydrogenase from cyanobacteria. Crude extracts from A. nidulans perform NAD(P)H-dependent H2 evolution corroborating the molecular biological demonstration of the NAD(P)(+)-dependent hydrogenase in cyanobacteria.

Alcaligenes↗

PubMed1995

Peptide-specific antibodies indicate species heterogeneity of a 42 kDa high-affinity inositol 1,3,4,5-tetrakisphosphate receptor protein from brain.

The aim of the present study was to identify a high affinity InsP4 receptor in membranes from cerebellum or brain from several species. In samples obtained from sheep, beef, human and rat, a 42 kDa protein represents an Ins(1,3,4,5)P4 receptor, similar to the InsP4 receptor from pig cerebellum, which we have described previously using an InsP4-photoaffinity analogue (Reiser et al., Biochem. J. 1991, 280, 533). CNBr cleavage of the pig receptor protein for peptide sequencing revealed peptide sequences which demonstrate that the 42 kDa InsP4 receptor is a novel protein. Two synthetic peptides derived from the pig receptor were used to generate peptide-specific antisera which recognized also the intact receptor protein from pig. The two antisera showed different reactivity with the InsP4 receptor purified from pig and human compared to sheep, beef, and rat. This indicates a species heterogeneity of this protein.

Amino Acid Sequence↗

PubMed1995

Characterization of a high-affinity Ins-P4 (inositol 1,3,4,5-tetrakisphosphate) receptor from brain by an anti-peptide antiserum.

From a high-affinity Ins-P4 (inositol 1,3,4,5-P4) receptor purified from pig cerebellum, digested with the protease Lys C peptide sequences were obtained. Synthetic peptide-3 (19 amino acid residues) was used to generate an antiserum. Reaction of the affinity-purified antibodies with the purified pig receptor protein in ELISA or Western blot was completely inhibited by peptide-3. In cerebellar membranes, the antibodies clearly recognized the 42 kDa Ins-P4 receptor protein and two additional proteins (25 kDa, 37 kDa) which still have to be identified. The anti-peptide antibodies could selectively immunoprecipitate the Ins-P4 receptor protein. The antiserum was used (i) to demonstrate that in brain from different species (human, pig, beef, rat, mouse and sheep) a similar 42 kDa Ins-P4 receptor protein is contained, and (ii) to obtain indications for the existence of a related soluble form of the 42 kDa Ins-P4 receptor besides the membrane-associated receptor.

Amino Acid Sequence↗

PubMed1995

Isolation of two interleukin-6 response element binding proteins from acute phase rat livers.

Proteins binding at the IL-6 response element of the rat alpha 2 macroglobulin gene were purified by a combination of conventional chromatographic procedures and binding-site specific DNA affinity chromatography. The proteins were purified from the nuclei of rat livers, excised at the peak of an experimentally induced acute phase response. By this procedure three polypeptides of 92, 91 and 86 kD were enriched more than 6,000-fold. Partial proteolysis with lysyl endopeptidase and aminoacid sequence analysis of proteolytic peptides identified the 86 and 91 kD species as the transcription factor Stat3 and the 92 kD species as a Stat factor distinct from Stats 1 and 3. cDNA clones for Stats 1, 3 and this 92 kD factor were isolated from a cDNA library prepared with mRNA from acute phase rat livers. Parts of their DNA sequences were determined and the sequences of the purified peptides were found in these cDNA sequences. Thus, the identity of the factors as Stat3 and a Stat factor different from Stats 1 and 3 was confirmed. These results suggest, that APRF/Stat3 and p91/Stat1 are not the only factors mediating the effects of IL-6 on class 2 acute phase genes. The 92 kD Stat factor binding at the IL-6 RE probably also functions as a transcription factor in the cytokine-induced activation of the alpha 2M gene.

Acute-Phase Reaction↗