Biomedical subjects

G Jung

Publications and source records attributed to G Jung.

At least 343 records · Page 19Linked to original sources

PubMed1993

Analysis of antibody response to the measles virus using synthetic peptides of the fusion protein. Evidence of non-random pairing of T and B cell epitopes.

The measles virus induces a life-long immune response associated with antibodies specific for the fusion protein. To map the linear immunodominant recognition sites of the fusion (F) protein of the measles virus, we have reacted a complete set of 108 overlapping pentadecapeptides with purified IgG obtained from donor sera with elevated anti-measles titers. The antibodies recognized about 20% of the peptides and generated a characteristic binding pattern, defining about 6 or 7 distinctive regions (31-75; 111-145; 151-165; 191-215; 271-320; 421-440; 481-530) which include the major hydrophobic segment (111-145) of the intersubunit region and the C-terminal Cys-cluster region. The binding sites were located in close proximity of the few experimentally defined T cell epitopes. This pairing of T and B cell epitopes was corroborated by computer-assisted T cell prediction. The significance of a non-random association of T and B cell epitopes for processing and presentation is discussed. It is speculated that in long-term immunity against measles (F protein), B cells of the same sIg specificity play an important role both as antigen presenting cells and as antibody producing cells. In contrast to human sera from late convalescent donors, mouse and rabbit MV antisera with high neutralizing titers as well as neutralizing MV-F specific monoclonal antibodies did not react with the peptides.

Adult↗

PubMed1993

Natural peptide ligand motifs of two HLA molecules associated with myasthenia gravis.

The peptide motifs of two HLA molecules, B8 and DR3(17), which are associated with autoimmune diseases including myasthenia gravis, were determined from natural peptide pools using Edman degradation. The majority of HLA-B8 ligands are nonamers preferentially terminated by leucine. As a characteristic feature of the HLA-B8 motif, there is a high degree of conservation of positively charged amino acids at position 3 and 5, exclusively lysine at position 3, and lysine or arginine at position 5. Additional evidence for this allele-specific motif is the presence of these features in several viral peptides recognized by HLA-B8 restricted T cells. The DR3(17) motif is characterized by four conserved anchor-like positions ordered in an almost symmetrical arrangement, as has been found for DR1 and DR5 motifs. A first hydrophobic/aromatic anchor three to four residues apart from the N-terminus (at relative position 1) appears to be a common feature of DR ligands. The second anchor is an aspartate at relative position 4, which is likely to be the DR3(17)-specific contact site in the groove. Two additional conserved positions closer to the C-terminus are occupied by charged amino acids at relative position 6 and by hydrophobic/aromatic residues at positions 8, 9, or 10. Eight individual naturally processed DR17 ligands were sequenced and were found to be derived from exogenous proteins and cytoplasmic membrane receptors. These natural peptides conform well to the determined motif. A single exchange of the anchor-like positions in a model peptide abrogated binding to DR17+ cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗

PubMed1993

Comparison of the H-2Kk- and H-2Kkm1-restricted peptide motifs.

Self-peptide pools eluted from purified H-2Kk or H-2Kkm1 molecules were sequenced. The majority of self-peptides associated with H-2Kk molecules were found to be octamers with two anchor positions. Position 2 is invariantly occupied with Glu, and the C-terminal residue at position 8 is almost always Ile. Comparison of this motif with synthetic peptides known to contain viral or parasite T-cell epitopes could be well aligned with this motif, except that the C-terminal Ile residue frequently appears to be at position 9 of the aligned sequences, instead of 8. Self-peptides eluted from mutant H-2Kkm1 molecules also appear to be mostly octamers with the same Ile residues at position 8 as with Kk. Position 2 is still dominantly occupied by Glu; in contrast to the Kk motif, however, Gln, Gly, and Pro are also allowed. Other differences between the two motifs indicate that a certain number of peptides presented by one of the molecules are not presented by the other.

Amino Acid Sequence↗

PubMed1993

Purification of yersiniabactin: a siderophore and possible virulence factor of Yersinia enterocolitica.

HPLC analysis revealed that Yersinia enterocolitica WA-C produced two substances under iron-limiting conditions one of which was identified as 2,3-dihydroxybenzoyl-L-serine. The other compound had iron-complexing activity and was called yersiniabactin. The fur mutant H1852 was shown to produce yersiniabactin constitutively in an iron-independent manner. Yersiniabactin was isolated by ethyl acetate extraction from the spent medium of H1852, size-fractionation chromatography and preparative HPLC. A catechol function was demonstrated with different chemical assays and by UV-visible spectroscopy. The molecular mass of yersiniabactin was determined to be 482 Da. Purified yersiniabactin stimulated growth of Y. enterocolitica and Escherichia coli phi under iron-limiting conditions and apparently served as an iron carrier. Transport of 55Fe-yersiniabactin was TonB-dependent, indicating a receptor-mediated uptake across the outer membrane. A pesticin-resistant mutant missing the receptor protein FyuA was unable to transport and use yersiniabactin as a siderophore.

Bacterial Outer Membrane Proteins↗

PubMed1993

Analysis of the neutralizing antibody response to the measles virus using synthetic peptides of the haemagglutinin protein.

Infection or immunization with measles virus induces a protective immune reaction including neutralizing antibodies against the haemagglutinin and fusion protein. The reactivity of the polyclonal IgG response of sera obtained from late convalescent donors was studied, using overlapping 15mer peptides covering the complete sequence of the measles virus haemagglutinin. Most sera reacted with a similar set of peptides generating a characteristic binding pattern. The reactive peptides correspond to a region mediating cell hemolysis (aa310-325), to regions which serve as targets to neutralizing antibodies and to a putative transmembrane region (aa35-58). The latter region contains also a human T-cell epitope providing evidence of a non-random association of T- and B-cell epitopes. We also immunized different strains of mice and rabbits with measles virus. In contrast to the human sera, animal sera with strong neutralizing activities did not react with any of the H-protein peptides. The mostly weak reactivities with the linear sequences contrast with the strong neutralizing activities of the human or animal antibodies, suggesting that these primarily recognize the fusion protein or conformational epitopes of the haemagglutinin protein.

Adult↗

PubMed1993

Alpha-keto acids are novel siderophores in the genera Proteus, Providencia, and Morganella and are produced by amino acid deaminases.

Growth promotion and iron transport studies revealed that certain alpha-keto acids generated by amino acid deaminases, by enterobacteria of the Proteus-Providencia-Morganella group (of the tribe Proteeae), show significant siderophore activity. Their iron-binding properties were confirmed by the chrome azurol S assay and UV spectra. These compounds form ligand-to-metal charge transfer bands in the range of 400 to 500 nm. Additional absorption bands of the enolized ligands at 500 to 700 nm are responsible for color formation. Siderophore activity was most pronounced with alpha-keto acids possessing an aromatic or heteroaromatic side chain, like phenylpyruvic acid and indolylpyruvic acid, resulting from deamination of phenylalanine and tryptophan, respectively. In addition, alpha-keto acids possessing longer nonpolar side chains, like alpha-ketoisocaproic acid or alpha-ketoisovaleric acid and even alpha-ketoadipic acid, also showed siderophore activity which was absent or negligible with smaller alpha-keto acids or those possessing polar functional groups, like pyruvic acid, alpha-ketobutyric acid, or alpha-ketoglutaric acid. The fact that deaminase-negative enterobacteria, like Escherichia coli and Salmonella spp., could not utilize alpha-keto acids supports the view that specific iron-carboxylate transport systems have evolved in members of the tribe Proteeae and are designed to recognize ferric complexes of both alpha-hydroxy acids and alpha-keto acids, of which the latter can easily be generated by L-amino acid deaminases in an amino acid-rich medium. Exogenous siderophores, like ferric hydroxamates (ferrichromes) and ferric polycarboxylates (rhizoferrin and citrate), were also utilized by members of the tribe Proteeae.

Amino Acids↗

PubMed1993

Cyclopeptide analogs for characterization of the neuropeptide Y Y2-receptor.

A discontinuous 17-amino acid peptide analog of neuropeptide Y (NPY), NPY 1-4-Ahx-25-36 containing 6-aminohexanoic acid instead of the residues 5 to 24, was found to bind preferentially to Y2 subtypes of NPY receptors. In order to further characterize the binding site, three different types of cyclic analogs were synthesized. Firstly lactamisation between residues 2 and 30 led to the most selective Y2-agonist, secondly lactamisation between the N-terminus and residue 31 reduced binding significantly. Thirdly, any cyclization including the C-terminus led to an inactive compound. Circular dichroism revealed different conformations for the three analogs with reduced alpha-helical content in comparison to the linear ana-log. The different conformation of the peptides has been confirmed by molecular dynamics simulations. A model for peptide-receptor interaction is suggested.

Amino Acid Sequence↗

PubMed1993

Helper T-cell recognition of HIV-1 Tat synthetic peptides.

The regulatory proteins coded by the human immunodeficiency virus, (HIV)-1 genome are expressed by the infected cells before the initiation of the synthesis of structural proteins and thus immune response directed against these proteins could destroy infected cells before the release of infectious virions. The evaluation of T-lymphocyte responses toward Tat, one of the main HIV-1 regulatory proteins, is therefore of interest. We selected a group of HIV-infected patients with retained response to the recall antigen purified protein derivative and tested their CD4+ helper T-cell response toward recombinant Tat and toward 12 soluble synthetic partially overlapping 15-16-mer Tat peptides in a proliferation assay. Three peptides (amino acids 17-32, 33-48, and 65-80) were significantly recognized by the helper T-cells from infected individuals but not by the nine HIV-1-negative control persons. Nine of the 14 patients (64%) responded to at least one of these Tat peptides. Of the identified immunodominant peptides containing T-cell epitopes, one (aa 65-80) was recognized in association with human leukocyte antigens DR-2 allele, while the others appeared to be promiscuous and were equally recognized in association with several DR molecules. The identified immunogenic peptides were analyzed for the predicted presence of T-cell antigenic sites by several algorithms and positive correlation was detected for each peptide. Our results thus indicate that Tat protein can induce a cell-mediated immune response and identify three peptides containing T-cell epitopes that may be of importance in vaccine development.

Alleles↗

PubMed1993

[Side reactions in peptide synthesis. V. O-sulfonation of serine and threonine during removal of pmc- and mtr-protecting groups from arginine residues in fmoc-solid phase synthesis].

A novel side reaction in Fmoc-solid-phase synthesis, which occurs during removal of protecting groups and detachment from the resin, was elucidated by investigations on model peptides: During the cleavage of Pmc- or Mtr-protecting groups from arginine residues by trifluoroacetic acid in peptides with O-tert-butyl-protected aliphatic hydroxyamino acids, peptides containing O3-sulfo-serine and O3-sulfo-threonine are formed as side-products in high yields, if suitable scavengers are absent. Subsequent to their isolation and purification, the structures of these peptide sulfuric acid mono-esters could unequivocally be proven by chemical and spectroscopic (MS, NMR, IR) methods.

Amino Acid Sequence↗

PubMed1992

Nucleocapsid protein of HIV-1 and its Zn2+ complex formation analysis with electrospray mass spectrometry.

The Zn2+ binding properties of the synthetic nucleocapsid protein (Ncp7) of HIV-1, containing two zinc-binding domains, have been studied using electrospray mass spectrometry (ES-MS). ES-MS measurements revealed strong binding of Zn2+ by Ncp7. Its shorter fragments, Ncp7-(1-35)- and (29-55)-peptides, each containing only one zinc-binding domain, bind one equivalent of Zn2+ ions tightly. ES-MS studies allows these fragments to be distinguished in terms of their binding affinity: they showed stronger binding of Zn2+ by Ncp7-(1-35)-peptide. Surprisingly, in addition to the expected two zinc-binding domains, a third metal binding site was detected in Ncp7. However, this site appears to bind different metal ions without selectivity and most probably reflects salt formation at the C-terminal acidic residues.

Amino Acid Sequence↗

PubMed1992

Molecular dynamics study of a complex between the human histocompatibility antigen HLA-A2 and the IMP58-66 nonapeptide from influenza virus matrix protein.

The structure of the influenza-virus-matrix-protein (IMP) 58-66 nonapeptide, bound to the major-histocompatibility-complex-encoded human leukocyte antigen (HLA) A2 protein was studied by molecular dynamics simulation. Starting from the extra electron density map of peptides co-crystallized with HLA-A2, the nonapeptide IMP58-66 was docked residue by residue in the protein binding cleft. The complex was simulated for 100 ps in a shell of 1372 water molecules. The averaged simulated HLA-A2 conformation was found to be similar to the crystal structure (0.182 nm RMS deviation, for the backbone atoms of the alpha 1-alpha 2 domain). Nine out of the 14 hydrogen bonds observed in the antigen-binding site were reproduced in the simulation. The IMP58-66 peptide exhibits an extended conformation with kinks at positions 3 and 5. The side chains of residues 2, 3 and 9 develop van der Waals' interactions with hydrophobic pockets of HLA-A2, corresponding to polymorphic residues of the major-histocompatibility-complex-encoded proteins. Both the N-terminus and C-terminus of the nonapeptide were anchored in the antigen-binding groove by hydrogen bonds with conserved amino acids. The N-terminus was more flexible and contacts four HLA-A2 conserved tyrosines (Tyr7, Tyr59, Tyr159 and Tyr171) and Glu63 by direct or water-relayed hydrogen bonds. Water intercalation occurred only around the N-terminus of the peptide, the C-terminal carboxylate forming strong hydrogen bonds with polar residues (Tyr84 and Thr143) and a salt bridge with Lys146 all over the molecular dynamics simulation. This model is fully compatible with the recently published crystal structure of the HLA-B27 protein, complexed by a mixture of self nonapeptides.

Amino Acid Sequence↗

PubMed1992

Investigation of the active site of Escherichia coli beta-D-galactosidase by photoaffinity labelling.

3,7-Anhydro-2-azi-1,2-dideoxy-D-glycero-L-manno-(8-3H)octitol++ + (1a) and 3-azibutyl 1-thio-beta-D-(6-3H)galactopyranoside (2a) were synthesised from the unlabelled compounds by reaction with galactose oxidase, then reduction with sodium borotritide. Whereas 1a was an efficient photoaffinity reagent for the beta-D-galactosidase from E. coli, 2a was ineffective. Three 3H-labelled peptides were isolated after digestion of the labelled enzyme with trypsin, one of which was an octapeptide (Trp 158 to Ser 165), which is remote from the segments detected as part of the active site of the enzyme.

Affinity Labels↗

PubMed1992

A novel cyclic analog of neuropeptide Y specific for the Y2 receptor.

The low-molecular-mass, cyclic analog of neuropeptide Y, [Ahx5-24, gamma-Glu2-epsilon-Lys30] NPY (YESK-Ahx-RHYINKITRQRY; Ahx, 6-aminohexanoic acid; NPY, neuropeptide Y), was synthesized and investigated for receptor binding, inhibition of forskolin-stimulated cAMP accumulation, inhibition of electrically stimulated rat vas deferens contractions and ability to increase blood pressure. Like the linear peptide [Ahx5-24] NPY (YPSK-Ahx-RHYINLITRQRY), the more rigid, cyclic analog showed good correlation between receptor binding to rabbit kidney membranes and biological activity in the vas deferens assay. Binding of this peptide to a new Y2-receptor-expressing cell line was slightly reduced, compared to the linear peptide [Ahx5-24] NPY, however inhibition of cAMP accumulation was even more efficient. Unlike the linear peptide [Ahx5-24] NPY, the cyclic analog did not induce a blood pressure increase in rats. Reduced binding to Y1 receptor-expressing SK-N-MC cells, as well as the loss of capability of signal transduction, suggest that only Y2-mediated activity is preserved after cyclization. The selectivity of the cyclic compound for Y2 subtypes of NPY receptors with respect to inhibition of cAMP accumulation is more than fortyfold increased, as compared to the linear NPY-(13-36) peptide, which has been used to determine Y2 selectivity so far.

Amino Acid Sequence↗

PubMed1992

Self-peptide released from class II HLA-DR1 exhibits a hydrophobic two-residue contact motif.

Peptide fragments of foreign and self-proteins are of great immunologic importance as their binding to major histocompatibility complex (MHC) class I or II molecules makes an interaction with a corresponding T cell receptor possible. Recently, allele-specific peptide sequence motifs proved to be responsible for MHC binding, no matter whether self- or non-self-antigens were involved. Up to now, all investigated human class II-associated peptides were derived from foreign antigenic proteins. Therefore, we undertook sequence and binding analyses with a 16-mer self-peptide (SP3) that has been eluted from HLA-DR1. Here we demonstrate, by synthetic polyalanine-based 13-mer analogues of SP3, that two bulky hydrophobic anchor residues with relative spacing i, i + 8 are sufficient for high affinity binding. This is consistent with the hydrophobic i, i + 8 binding pattern recently found for DR-restricted T cell epitopes. Nevertheless, highly helical alanine-based design peptides with anchor spacing i, i + 9 exhibit maximal affinity, whereas replacement of alanine by helix destabilizing proline abrogates binding. Thus, a two-residue contact motif is the common minimal requirement of self- and foreign peptides for high affinity anchoring to HLA-DR1. In contrast to class I, the anchor spacing of DR1-associated peptides seems to bear some variability due to conformational diversity.

Amino Acid Sequence↗

PubMed1992

Neuropeptide Y. Optimized solid-phase synthesis and conformational analysis in trifluoroethanol.

The 36-amino-acid neuropeptide Y (human), which is one of the most potent vasoconstrictors and which exhibits a number of other biological functions, has been synthesized using automated peptide synthesis. The optimized method, using 9-fluorenylmethoxycarbonyl protecting and single-step coupling, yielded the crude product in 90% purity allowing for single-step reversed-phase HPLC purification to greater than 98% purity and a high overall yield (50%). The hormone was characterized by several chromatographic methods, ion-spray mass spectroscopy and Edman degradation. The conformation of human neuropeptide Y was examined by CD, NMR and computer simulations. The CD measurements in trifluoroethanol/water (9:1) show a large percentage of alpha-helix. Variation of concentration, from 0.5 microM increasing up to the 1 mM used for NMR measurements, indicates no evidence for aggregation. In the same solvent system, the NMR line widths were very broad and therefore the resonance assignment was achieved with the exclusive use of two-dimensional NOE spectra. The 248 clearly distinguishable NOEs from the NMR study were used in distance geometry calculations and the resulting structures were refined with restrained molecular dynamics. The results indicate an alpha-helix extending from Arg19 to Gln34. For the N-terminal half of the molecule no regular structure was observed.

Amino Acid Sequence↗

PubMed1992

Lipopeptides are effective stimulators of tyrosine phosphorylation in human myeloid cells.

Synthetic lipopeptide analogues of the N-terminus of bacterial lipoprotein are effective activators of macrophages, neutrophils and lymphocytes. We studied the effect of the lipopeptide N-palmitoyl-S-[2,3-bis(palmitoyloxy)-(2RS)-propyl]- (R)-cysteinyl-(S)-seryl-(S)-lysyl-(S)-lysyl-(S)-lysyl-(S)-lysine [Pam3Cys-Ser-(Lys)4] on tyrosine phosphorylation in dibutyryl-cyclic-AMP-differentiated HL-60 cells, using anti-phosphotyrosine antibodies. Pam3Cys-Ser-(Lys)4 concentration-dependently stimulated tyrosine phosphorylation of 100/110 kDa and 60 kDa proteins and, to a lesser extent, of 55 kDa and 70/75 kDa proteins. Half-maximal and maximal effects were observed at concentrations of 1-6 and 5-50 micrograms/ml respectively. The lipopeptide-induced increase in phosphorylation was rapid and transient, with a peak response after 30-60 s. The lipopeptide (2S)-2-palmitoylamino-6-palmitoyloxymethyl-7-palmitoyloxy heptanoyl-Ser-(Lys)4 [Pam3Ahh-Ser-(Lys)4] was as potent as Pam3Cys-Ser(Lys)4, whereas (2S,6S)-2-palmitoylamino-6,7-bis(palmitoyloxy)heptanoyl++ +-Ser-(Lys)4 [Pam3Adh-Ser-(Lys)4] and Pam3Cys-Ser-Gly did not induce tyrosine phosphorylation. Lipopeptide-induced tyrosine phosphorylation was not affected by treatment of cells with pertussis toxin. Neither phorbol 12-myristate 13-acetate nor A23187 induced tyrosine phosphorylation in dibutyryl-cyclic-AMP-differentiated HL-60 cells. In HL-60 promyelocytes, Pam3Cys-Ser-(Lys)4 had no effect on tyrosine phosphorylation, whereas the lipopeptide also induced tyrosine phosphorylation in 1,25-dihydroxyvitamin-D3-differentiated HL-60 cells and in human neutrophils. These results show that lipopeptides are effective stimulators of tyrosine phosphorylation in mature human myeloid cells.

Blotting, Western↗

PubMed1992

Incomplete functional differentiation of HL-60 leukemic cells by synthetic lipopeptides. Partial inhibition by pertussis toxin of enhanced superoxide formation.

In human neutrophils, the synthetic lipopeptide, N-palmitoyl-S-[2,3- bis(palmitoyloxy-(2RS)-propyl]-(R)-cysteinyl-(S)-seryl-(S)-lysyl-( S)-lysyl-(S) -lysyl-(S)-lysine [Pam3CysSer(Lys)4], activates NADPH-oxidase catalyzed superoxide (O2-) formation through pertussis-toxin-sensitive and pertussis-toxin-insensitive mechanisms (Seifert, R., Schultz, G., Richter-Freund, M., Metzger, J., Wiesmüller, K.-H., Jung, G., Bessler, W. G. & Hauschildt, S. (1990) Biochem. J. 267, 795-802). We studied the effects of lipopeptides on differentiation of HL-60 leukemic cells. Pam3CysSer(Lys)4 enhanced phorbol-12-myristate-13-acetate-induced O2- formation (presumably through the expression of components of NADPH oxidase) in a concentration-dependent manner with a half-maximal effect at 100 ng/ml and a maximum at 1 microgram/ml. The effect of the lipopeptide was evident after 24 h and reached a plateau after 48 h. (2S,6S)-2-Palmitoylamino-6,7- bis(palmitoyloxy)heptanoyl-(S)-seryl-(S)-lysyl-(S)-lysyl-(S) -lysyl-(S)-lysine enhanced O2- formation as well. The effects of Pam3CysSer(Lys)4 were potentiated by dibutyryl cAMP, dimethyl sulfoxide, retinoic acid, 1,25-dihydroxyvitamin D3, interferon-gamma and tumor-necrosis-factor-alpha. Pertussis toxin, but not its B-oligomer, partially inhibited enhanced O2- formation induced by Pam3CysSer(Lys)4. O2- formation induced by arachidonic acid and gamma-hexachlorocyclohexane were more sensitive to inhibition by pertussis toxin than O2- formation induced by phorbol 12-myristate 13-acetate. Enhanced O2- formation induced by dibutyryl cAMP was not affected by pertussis toxin. Unlike ATP, histamine, prostaglandin E1 and the beta-adrenergic agonist, isoproterenol, Pam3CysSer(Lys)4 did not increase cytosolic Ca2+ [( Ca2+]i) in undifferentiated HL-60 cells. Histamine but not lipopeptides stimulated high-affinity GTPase of guanine-nucleotide-binding proteins in membranes of undifferentiated HL-60 cells. In Pam3CysSer(Lys)4-differentiated HL-60 cells, the responsiveness to the [Ca2+]i-increasing agonists, N-formyl-L-methionyl-L-leucyl-L-phenylalanine, C5a and leukotriene B4, was increased, whilst the responsiveness to prostaglandin E1 and isoproterenol was decreased. Pam3CysSer(Lys)4 did not inhibit proliferation of HL-60 cells but decreased transferrin receptor expression and increased C3bi receptor expression. Pertussis toxin did not affect proliferation and expression of transferrin and C3bi receptors. Dibutyryl cAMP was considerably more effective than Pam3CysSer(Lys)4 at inducing alterations in the above parameters. Our results suggest that (a) Pam3CysSer(Lys)4 induces incomplete functional differentiation of HL-60 cells through a mechanism which does not depend on a rise in [Ca2+]i and is different from that of other differentiation-inducing substances and (b) the mechanism by which Pam3CysSer(Lys)4 induces differentiation involves pertussis-toxin-sensitive and pertussis-toxin-insensitive mechanisms.

Bucladesine↗

PubMed1992

Preferred size of peptides that bind to H-2 Kb is sequence dependent.

The identification of naturally processed viral peptides reveals that major histocompatibility complex (MHC) class I epitopes are composed of nine or eight amino acid residues. Peptides eluted from H-2 Kb MHC class I molecules have been suggested, as a class, to be eight amino acid residues long. To assay for peptide-class I interactions, a stabilization assay described for surface labeled "empty" class I molecules was employed, but on biosynthetically labeled class I molecules. The Sendai virus nucleoprotein-derived octapeptide APGNYPAL does not bind and stabilize Kb molecules, whereas other octameric Kb-restricted peptides and the nonameric peptide FAPGNYPAL interact stably. We attribute the failure of Sendai octamer binding to the presence of proline in position two: replacement of proline renders the resulting octamers as efficient as FAPGNYPAL for binding and stabilization of H-2 Kb. Substitution of glycine in position three of APGNYPAL slightly improves its Kb stabilizing capacity. Iodination of the tyrosine residue significantly alters the binding properties of the nonamer peptide. We conclude that the length of epitopes as selected by the class I Kb molecule is influenced by their sequence and suggest that proper positioning of the NH2 terminus of peptides is essential for class I stabilizing properties. The ability to stabilize newly synthesized "empty" class I molecules with peptide argues against an involvement of beta 2 microglobulin exchange in the experiments described here.

Amino Acid Sequence↗