Biomedical subjects

H Gausepohl

Publications and source records attributed to H Gausepohl.

At least 19 recordsLinked to original sources

PubMed1997

Hybridisation based DNA screening on peptide nucleic acid (PNA) oligomer arrays.

Arrays of up to some 1000 PNA oligomers of individual sequence were synthesised on polymer membranes using a robotic device originally designed for peptide synthesis. At approximately 96%, the stepwise synthesis efficiency was comparable to standard PNA synthesis procedures. Optionally, the individual, fully deprotected PNA oligomers could be removed from the support for further use, because an enzymatically cleavable but otherwise stable linker was used. Since PNA arrays could form powerful tools for hybridisation based DNA screening assays due to some favourable features of the PNA molecules, the hybridisation behaviour of DNA probes to PNA arrays was investigated for a precise understanding of PNA-DNA interactions on solid support. Hybridisation followed the Watson-Crick base pairing rules with higher duplex stabilities than on corresponding DNA oligonucleotide sensors. Both the affinity and specificity of DNA hybridisation to the PNA oligomers depended on the hybridisation conditions more than expected. Successful discrimination between hybridisation to full complementary PNA sequences and truncated or mismatched versions was possible at salt concentrations down to 10 mM Na+and below, although an increasing tendency to unspecific DNA binding and few strong mismatch hybridisation events were observed.

Carbohydrate Sequence↗

PubMed1997

Automated protein preparation techniques using a digest robot.

Since the introduction of fast analysis methods for peptide mixtures such as MALDI-MS, peptide micropreparation and digest methods have become an important bottleneck in the protein characterization process. We therefore developed and describe here a digest robot capable of processing 30 protein samples in parallel [Houthaeve et al. (1995), FEBS Lett. 376, 91-94]. Briefly, after gel pieces or blots are cut out, they are loaded in flowthrough reactors and these are loaded in a thermocontrolled reactor block. The proteins are then washed, reduced, and alkylated, proteolytically or chemically cleaved, and resulting peptides extracted. The system allows the parallel use of different reagents and enzymes during the same run, and is compatible with RP-HPLC peptide separation and Edman degradation, MALDI-MS, and NanoES-MS/MS. The digest robot is now also commercially available from ABIMED. In an ongoing project aimed at elucidating proteinaceous structures involved in the functional and structural maintenance of the Golgi apparatus, we illustrate the strength of the digest robot for the fast analysis of several proteins. We conclude that the performance of the digest robot is comparable to currently used manual digestion methods. The approach outlined makes sample preparation procedures faster, simpler, and less labor-intensive.

Chemistry Techniques, Analytical↗

PubMed1995

Automation of micro-preparation and enzymatic cleavage of gel electrophoretically separated proteins.

To achieve high throughput, protein microcharacterization sample preparation must be automated. We describe a cartesian robot capable of processing 32 protein samples in parallel. The system is based on specially designed flow-through reactors for contamination-free reagent delivery and removal. Washing of excised gel pieces, reduction and alkylation, proteolytic cleavage and peptide extraction are performed in these reactors. Compatibility of the system with HPLC peptide separation and Edman degradation as well as with laser desorption mass spectrometry of the unseparated mixture is demonstrated. This is the first report describing automated preparation and processing of multiple protein samples.

Amino Acid Sequence↗

PubMed1992

Identification of T cell epitopes occurring in a meningococcal class 1 outer membrane protein using overlapping peptides assembled with simultaneous multiple peptide synthesis.

The meningococcal class 1 outer membrane protein (OMP) plays an important role in the development of protective immunity against meningococcal infection, and is therefore considered to be a promising candidate antigen (Ag) for a meningococcal vaccine. The induction of an effective antibody response entirely depends upon T helper cells. To identify T cell epitopes of the OMP, we prepared 45 overlapping synthetic peptides representing the entire sequence of the class 1 protein of reference strain H44/76. Fully automated simultaneous multiple peptide synthesis (SMPS) was used to assemble the 45 twenty mer which overlapped by 12 amino acid residues on a 12 mumol scale. The peptides were tested for recognition by peripheral blood mononuclear cells (PBMC) obtained from 34 volunteers. Surprisingly, all synthetic peptides induced proliferative responses of PBMC isolated from one or more human histocompatibility leukocyte antigen (HLA)-typed immune adults. With PBMC from seven nonimmune donors, no proliferative response was observed. Immunodominant regions were found, recognized by PBMC from many volunteers, irrespective of their HLA type. Most of the immunodominant T cell epitopes are located outside the variable regions and, thus, will be conserved among different meningococcal (and gonococcal) strains. Furthermore, the overlapping peptides could be used to identify the epitopes recognized by OMP-specific T cell clones with known HLA restriction. It is interesting that the epitopes defined with the clones occur in highly conserved areas, shared by all neisserial porin proteins. In summary, this analysis of the T cell response to the meningococcal class 1 OMP constitutes a complete study of reactivity to a foreign protein, and illustrates some important features of Ag recognition by T cells. Our data demonstrate unexpected diversity in the T cell recognition of the OMP, and imply that the T cell repertoire against foreign Ag may be greater than previously assumed. This observation is supported by recent data on the interaction of peptide and major histocompatibility complex (MHC) class II, the latter being much less selective than MHC class I. Finally, a comparative analysis pointed out the limitations of algorithms predicting T cell determinants, and the importance of the empirical methodology provided by SMPS.

Adult↗

PubMed1992

Generation of specific antibodies against the rap1A, rap1B and rap2 small GTP-binding proteins. Analysis of rap and ras proteins in membranes from mammalian cells.

Specific antibodies against rap1A and rap1B small GTP-binding proteins were generated by immunization of rabbits with peptides derived from the C-terminus of the processed proteins. Immunoblot analysis of membranes from several mammalian cell lines and human thrombocytes with affinity-purified antibodies against rap1A or rap1B demonstrated the presence of multiple immunoreactive proteins in the 22-23 kDa range, although at strongly varying levels. Whereas both proteins were present in substantial amounts in membranes from myelocytic HL-60, K-562 and HEL cells, they were hardly detectable in membranes from lymphoma U-937 and S49.1 cyc- cells. Membranes from human thrombocytes and 3T3-Swiss Albino fibroblasts showed strong rap1B immunoreactivity, whereas rap1A protein was present in much lower amounts. In the cytosol of HL-60 cells, only small amounts of rap1A and rap1B proteins were detected, unless the cells were treated with lovastatin, an inhibitor of hydroxymethylglutaryl-coenzyme A reductase, suggesting that both proteins are isoprenylated. By comparison with recombinant proteins, the ratio of rap1A/ras proteins in membranes from HL-60 cells was estimated to be about 4:1. An antiserum directed against the C-terminus of rap2 reacted strongly with recombinant rap2, but not with membranes from tested mammalian cells. In conclusion, rap1A and rap1B proteins are distributed differentially among membranes from various mammalian cell types and are isoprenylated in HL-60 cells.

Amino Acid Sequence↗

PubMed1992

Immunological characterization of an immunomodulatory epitope in S-antigen/arrestin with a sequence motif common to tumor necrosis factor alpha.

Some monoclonal antibodies (mAbs) to retinal S-antigen recognize a phylogenetically conserved epitope (S2) in the N-terminal part of the protein. These antibodies have been shown to inhibit the induction of experimental autoimmune uveoretinitis by S-antigen in rats. Using Pepscan method, we localized this epitope on the amino acid (aa) residues 40-50, i.e., PVDGVVLVDPE (peptide S2). MAb binding was confirmed by ELISA, competition-ELISA and dot blot. Other S-antigen peptides with homologies to epitope S2 and peptides exhibiting the pathogenic and T-cell proliferation inducing sites did not bind these mAbs. Epitope S2 displays an immunological crossreactivity with human tumor necrosis factor (TNF) alpha. Recent results indicate that both peptide S2 and a peptide from human TNF alpha (aa residues 31-53) containing the common sequence motif GVxLxD induce TNF alpha production in monocytes. We analyzed the fine structure of the common epitope by studying mAb binding in an amino acid residue exchange experiment.

Amino Acid Sequence↗

PubMed1992

A common epitope on human tumor necrosis factor alpha and the autoantigen 'S-antigen/arrestin' induces TNF-alpha production.

A common epitope on S-antigen (arrestin), a potent autoantigen inducing experimental autoimmune uveoretinitis (EAU), and on human tumor necrosis factor alpha (hTNF alpha) was revealed using two monoclonal antibodies to S-antigen which inhibit EAU induction. The minimal common sequence for monoclonal antibody recognition is GVxLxD in the S-antigen/hTNF alpha amino acid sequences. Peptides containing this sequence motif exhibited monocyte activating capacity similar to the autocrine stimulatory capacity of hTNF alpha itself. In the S-antigen this activity was located from residue 40 to 50, corresponding to the peptide PVDGVVLVDPE (epitope S2). In hTNF alpha, the monocyte activating capacity correlated to residue 31 to 53, corresponding to the peptide RRANALLANGVELRDNQLVVPSE (peptide RRAN). The identified regions define common functional structures in the autoantigen and in the hTNF alpha molecule. The data suggest a regulatory function of this particular structure in TNF alpha expression and in autoimmunity.

Amino Acid Sequence↗

PubMed1992

Definition of immunogenic determinants of the human papillomavirus type 16 nucleoprotein E7.

Specific T lymphocyte lines and T cell clones were established from peripheral blood mononuclear cells of asymptomatic seropositive individuals employing synthetic peptides which correspond to the sequence of the human papillomavirus (HPV) type 16 transforming protein E7. Specificity analysis of T cells as determined by means of [3H] thymidine incorporation after stimulation with individual peptides revealed three immunogenic determinants of E7 that are recognised in association with at least two different HLA haplotypes. One N-terminal region (aminoacids 5-18) was recognised by one T cell line. T cell clones and the corresponding T cell line established from another donor responded to a different N-terminal (17-38) and to a C-terminal region (69-86). The N-terminal sequence 5-18 and the C-terminal determinant contain a periodicity of hydrophilic and hydrophobic residues that have been found in many T cell epitopes. Phenotypic characterisation of T cell clones by indirect immunofluorescence revealed that the T cell clones expressed the CD4 surface glycoprotein suggesting that the specific E7 determinants were recognised in association with major histocompatibility complex (MHC) class II molecules. With regard to functional properties, at least three T cell clones exhibited specific cytotoxic activity towards autologous B lymphocytes transformed by Epstein-Barr virus in the presence of the relevant HPV16 E7 peptides. The implications of these results regarding the development of vaccination strategies and host-virus interaction are discussed.

Amino Acid Sequence↗

PubMed1992

Cytokine induction by immunomodulatory epitopes in S-antigen and tumor necrosis factor alpha.

Common epitopes on S-antigen (arrestin), a potent autoantigen inducing experimental autoimmune uveoretinitis (EAU), and on human tumor necrosis factor alpha (hTNF alpha) are revealed with monoclonal antibodies (mAb) to S-antigen, which inhibit EAU induction. The minimal common sequence for mAb recognition is GVxLxD in the S-antigen/hTNF alpha amino acid (aa) sequences. Peptides containing this sequence motif exhibit monocyte activating capacity analogous to the autocrine stimulatory capacity of hTNF alpha itself. In S-antigen this activity is located at epitope S2 (aa residues 40 to 50), corresponding to the peptide PVDGVVLVDPE (peptide S2). In hTNF alpha the monocyte activating capacity correlates to aa residue 31 to 53, corresponding to the peptide RRANALLANGVELRDNQLVVPSE (peptide RRAN). Peptide S2 but not peptide RRAN is competing for mAbs S6H8 and S2D2 binding to S-antigen. Anti-idiotypic antibodies to S2D2 compete with peptide S2 but not peptide RRAN for binding to mAbs S2D2 and S6H8. In human retinal S-antigen epitope S2 is localized at the aa residues 44-54 and is cleaved in the human peptide 4 (aa 31-50). Competition experiments with peptide 4 (aa 31-50) and peptide 5 (aa 41-60) indicate that the C-terminal aa residues VDPD in the epitope S2 play an important role for internal image recognition of the anti-idiotypic antibodies. Peptide S2 and peptide RRAN define common functional structures in the autoantigen and hTNF alpha molecules. The data suggest regulatory functions of the peptides in cytokine expression, network regulation and in autoimmunity.

Amino Acid Sequence↗

PubMed1991

Involvement of pertussis toxin-sensitive G-proteins in the hormonal inhibition of dihydropyridine-sensitive Ca2+ currents in an insulin-secreting cell line (RINm5F).

Adrenaline inhibits insulin secretion via pertussis toxin-sensitive mechanisms. Since voltage-dependent Ca2+ currents play a key role in insulin secretion, we examined whether adrenaline modulates voltage-dependent Ca2+ currents of the rat insulinoma cell line, RINm5F. In the whole-cell configuration of the patch-clamp technique, dihydropyridine- but not omega-conotoxin-sensitive Ca2+ currents were identified. Adrenaline via alpha 2-adrenoceptors inhibited the Ca2+ currents by about 50%. Somatostatin which also inhibits insulin secretion was less efficient (inhibition by 20%). The hormonal inhibition of Ca2+ currents was not affected by intracellularly applied cAMP but blocked by the intracellularly applied GDP analog guanosine 5'-O-(2-thiodiphosphate) and by pretreatment of cells with pertussis toxin. In contrast to adrenaline and somatostatin, galanin, another inhibitor of insulin secretion, reduced Ca2+ currents by about 40% in a pertussis toxin-insensitive manner. Immunoblot experiments performed with antibodies generated against synthetic peptides revealed that membranes of RINm5F cells possess four pertussis toxin-sensitive G-proteins including Gi1, Gi2, Go2, and another Go subtype, most likely representing Go1. In membranes of control but not of pertussis toxin-treated cells, adrenaline via alpha 2-adrenoceptors stimulated incorporation of the photo-reactive GTP analog [alpha-32P]GTP azidoanilide into pertussis toxin substrates comigrating with the alpha-subunits of Gi2, Go2, and the not further identified Go subtype. The present findings indicate that activated alpha 2-adrenoceptors of RINm5F cells interact with multiple G-proteins, i.e. two forms of Go and with Gi2. These G-proteins are likely to be involved in the adrenaline-induced inhibition of dihydropyridine-sensitive Ca2+ currents and in other signal transduction pathways contributing to the adrenaline-induced inhibition of insulin secretion.

Animals↗

PubMed1991

Solution structure of the basic region from the transcriptional activator GCN4.

The structure of the basic region (i.e., the region responsible for sequence-specific binding to DNA) of the transcriptional activator GCN4 was studied. Two peptide fragments containing either the basic region alone (residues 240-280) or the basic and the dimerization leucine zipper domains (220-280) were synthesized and investigated by nuclear magnetic resonance and circular dichroic spectroscopy. The basic region in the absence of DNA appears as a mobile flexible segment folded into a loose helix. The helical stability increases upon addition of trifluoroethanol and/or lowering of the temperature. Dimerization via the leucine zipper does not affect the three-dimensional structure of the basic region. Possible consequences for the binding to DNA are discussed.

Amino Acid Sequence↗

PubMed1991

Identification of a major human immunodeficiency virus-1 reverse transcriptase epitope recognized by mouse CD4+ T lymphocytes.

Delineation of major T helper cell recognition sites of human immunodeficiency virus (HIV-1) proteins represents one important step in the design of an efficient acquired immune deficiency syndrome (AIDS) vaccine. Towards this end, we have explored the immunogenicity of HIV-1BRU proteins in the mouse model. Preliminary experiments revealed that inbred mice primed with whole inactivated HIV-1 developed strong CD4+ T cell proliferative responses to a variety of recombinant viral proteins including reverse transcriptase (RT). To characterize further the mouse T cell responses to this protein, several Ad- or Ed-restricted T hybridoma cells (THC) were established from BALB/c or DBA/2 mice. These THC were tested for their capacity to recognize a series of 15-mer synthetic overlapping peptides spanning three segments of HIV-1 RT that had been preselected on the basis of either alpha-helicity, amphipaticity, and/or for containing rare amino acid sequence patterns. Peptides corresponding to a C-terminal region (residues 528-560) of RT were recognized by several of the THC established from RT-primed mice. Furthermore, a non-alpha-helical peptide from this region (A3, 528-543) was capable of priming mice with different H-2 haplotypes for both peptide A3 and native RT CD4+ T cell recognition. In addition to the recently identified RT determinant 203-219 capable of triggering both mouse and human CD8+ CTL, the present results identify a good candidate for an immunodominant RT epitope capable of eliciting RT-specific T helper cell responses.

Animals↗

PubMed1991

The solution structure of a leucine-zipper motif peptide.

We report the complete structure determination of a 34 residue synthetic peptide with the amino acid sequence of the dimerization domain (leucine zipper) of GCN4. A high resolution structure in solution was obtained by 1H-NMR studies and distance geometry calculations followed by restrained energy minimization. A set of 20 final structures was obtained with an average root mean square deviation of 1.3 A for the backbone atoms (excluding the first and the last two residues). The structure contains an uninterrupted helix. A comparison with a structure previously determined for a larger peptide containing both the DNA-binding region (basic region) and the leucine-zipper motif shows the structural independence of the leucine-zipper domain from the contiguous DNA binding region.

Amino Acid Sequence↗

PubMed1991

Human papillomavirus type 18 E6 and E7 antibodies in human sera: increased anti-E7 prevalence in cervical cancer patients.

Antibody-reactive regions on the human papillomavirus type 18 (HPV-18) E6 and E7 proteins were identified with rabbit polyclonal anti-fusion protein sera by screening of an fd phage expression library containing subgenomic HPV-18 DNA fragments and by testing of overlapping decapeptides representing the E6 and E7 open reading frames. Peptides comprising the delineated regions (designated E6/1 to E6/4 and E7/1) were synthesized and used in an enzyme-linked immunosorbent assay (ELISA) to detect anti-HPV-18 antibodies in human sera. A total of 232 human serum samples (identical numbers of cervical cancer patients and age-matched controls) collected in Tanzania were tested. Similar prevalences (between 0.8 and 4.3%) of antibodies recognizing the different E6 peptides were found in the sera from tumor patients and controls. With a synthetic 28-mer peptide (designated pepE701) comprising the E7/1 region, a significant difference was found: 10 of 116 tumor serum samples but 0 of 116 control serum samples showed a specific reaction (P less than 0.001). This observation confirms earlier results with HPV-16 E7 fusion proteins (I. Jochmus-Kudielka, A. Schneider, R. Braun, R. Kimmig, U. Koldovsky, K. E. Schneweis, K. Seedorf, and L. Gissmann, J. Natl. Cancer Inst. 81:1698-1704, 1989). A lower prevalence of anti-HPV-18 E7 antibodies was observed when 188 human serum samples collected in Germany from tumor patients and controls were tested (3 of 94 positive in the cancer group; 0 of 94 positive in the control group). The type specificity of anti-HPV-18 E7 antibodies was demonstrated when the HPV type found by Southern hybridization in the cervical cancer biopsies was compared with seroreactivity: 4 of 8 serum samples obtained from HPV-18 DNA-positive but 0 of 16 serum samples from HPV-18 DNA-negative tumor patients reacted in the HPV-18 E7 ELISA. In addition, HPV-18-positive sera failed to react in a peptide ELISA with the homologous HPV-16 E7 region (M. Müller, H. Gausepohl, G. de Martinoff, R. Frank, R. Brasseur, and L. Gissmann, J. Gen. Virol. 71:2709-2717, 1990) and vice versa.

Amino Acid Sequence↗

PubMed1990

Purification of soluble guanylyl cyclase from bovine lung by a new immunoaffinity chromatographic method.

Soluble guanylyl cyclase was purified from bovine lung by an immunoaffinity chromatographic method using IgG fractions of antisera against a synthetic peptide of the C-terminus of the 70-kDa subunit of the enzyme. After anion-exchange chromatography, the enzyme was bound to an immunoaffinity column and was eluted with the synthetic peptide. This method allowed the convenient isolation of 2 mg of apparently homogeneous enzyme from 40 g cytosolic proteins. The enzyme had an apparent molecular mass of about 150 kDa and consisted of two subunits (70 kDa and 73 kDa) as determined by gel permeation fast protein liquid chromatography and SDS/PAGE. The basal activities determined in the presence of Mg2+ and Mn2+ were 10-20 nmol.min-1.mg-1 and 80-100 nmol.min-1.mg-1, respectively. The enzyme exhibited an ultraviolet-visible absorption spectrum typical for hemoproteins, with a Soret band at 430 nm. The purified enzyme was stimulated by NO-containing compounds. Maximal enzyme activities measured in the presence of sodium nitroprusside were 1.2-2.4 mumol.min-1.mg-1 (half-maximal effect of sodium nitroprusside at 1.3-1.9 microM) and 0.9-1.8 mumol.min-1.mg-1 (half-maximal effect at 0.28-0.41 microM sodium nitroprusside) in the presence of Mg2+ and Mn2+, respectively. The method developed for the large-scale purification of soluble guanylyl cyclase by immunoaffinity chromatography, using synthetic peptides for the elution of the enzyme, appears to be superior to previously described methods. As antibodies against synthetic peptides corresponding to deduced amino acid sequences of the respective protein are easily obtained, the described method may be suitable for a convenient large-scale purification of various proteins.

Animals↗

PubMed1990

NMR and molecular dynamics studies of the mKr2 'zinc finger'.

We determined the structure of a 30-amino-acid 'zinc finger' motif from the mouse Kruppel-like gene mKr2 in solution in the absence of metal ions by two-dimensional NMR, distance geometry and restrained molecular dynamics methods. The most prominent secondary structural feature of the peptide is a helix extending from Ser14 to Ile20. The zinc-containing structure of the peptide was simulated by molecular dynamics calculations with restraints derived from the known geometry of the zinc ion and the ligating amino acid residues Cys6, Cys9, His22, His26. The latter structure does not deviate markedly from the set of structures determined for the zinc-free peptide, i.e. this peptide can accommodate a Zn2+ ion without major structural rearrangements. Thus, we propose that the metal ion stabilizes the existing three-dimensional peptide structural motif rather than introducing novel structural features.

Amino Acids↗

PubMed1990

The 54-kD protein of signal recognition particle contains a methionine-rich RNA binding domain.

Signal recognition particle (SRP) plays the key role in targeting secretory proteins to the membrane of the endoplasmic reticulum (Walter, P., and V. R. Lingappa. 1986. Annu. Rev. Cell Biol. 2:499-516). It consists of SRP7S RNA and six proteins. The 54-kD protein of SRP (SRP54) recognizes the signal sequence of nascent polypeptides. The 19-kD protein of SRP (SRP19) binds to SRP7S RNA directly and is required for the binding of SRP54 to the particle. We used deletion mutants of SRP19 and SRP54 and an in vitro assembly assay in the presence of SRP7S RNA to define the regions in both proteins which are required to form a ribonucleoprotein particle. Deletion of the 21 COOH-terminal amino acids of SRP19 does not interfere with its binding to SRP7S RNA. Further deletions abolish SRP19 binding to SRP7S RNA. The COOH-terminal 207 amino acids of SRP54 (M domain) were found to be necessary and sufficient for binding to the SRP19/7S RNA complex in vitro. Limited protease digestion of purified SRP confirmed our results for SRP54 from the in vitro binding assay. The SRP54M domain could also bind to Escherichia coli 4.5S RNA that is homologous to part of SRP7S RNA. We suggest that the methionine-rich COOH terminus of SRP54 is a RNA binding domain and that SRP19 serves to establish a binding site for SRP54 on the SRP7S RNA.

Animals↗

PubMed1990

Solution structure of the DNA-binding domain of the yeast transcriptional activator protein GCN4.

The solution structure of an active synthetic peptide containing both the leucine zipper and the adjacent basic domain of the yeast transcription factor GCN4 (residues 220-280) was determined by NMR. The two domains show structurally distinct behaviours. In the absence of DNA, the basic domain is, although very flexible, structured and fluctuating around a helical conformation. The leucine zipper region forms a long, uninterrupted helix. From a suitable set of NMR distances the three-dimensional structure of the leucine zipper monomeric sub-domain was calculated by distance geometry algorithms. The structure of the symmetrical parallel dimer was obtained by model building using the NMR information. A smaller peptide with the sequence of the isolated basic region (residues 1-35 of the 61 residue peptide) was also synthesized. Circular dichroism studies showed 30-40% helicity. A flexible helix spans the region between residues 8 and 21. The comparison of our results with suggested models is discussed in detail.

Algorithms↗