Biomedical subjects

Martin Hülsmeyer

Publications and source records attributed to Martin Hülsmeyer.

9 recordsLinked to original sources

PubMed2005

Thermodynamic and structural equivalence of two HLA-B27 subtypes complexed with a self-peptide.

The F pocket of major histocompatibility complex (in humans HLA) class I molecules accommodates the C terminus of the bound peptide. Residues forming this pocket exhibit considerable polymorphism, and a single difference (Asp116 in HLA-B*2705 and His116 in HLA-B*2709 heavy chains) confers differential association of these two HLA-B27 subtypes to the autoimmune disease ankylosing spondylitis. As peptide presentation by HLA molecules is of central importance for immune responses, we performed thermodynamic (circular dichroism, differential scanning calorimetry, fluorescence polarization) and X-ray crystallographic analyses of both HLA-B27 subtypes complexed with the epidermal growth factor response factor 1-derived self-peptide TIS (RRLPIFSRL) to understand the impact of the Asp116His exchange on peptide display. This peptide is known to be presented in vivo by both subtypes, and as expected for a self-peptide, TIS-reactive cytotoxic T lymphocytes are absent in the respective individuals. The thermodynamic analyses reveal that both HLA-B27:TIS complexes exhibit comparable, relatively high thermostability (Tm approximately 60 degrees C) and undergo multi-step unfolding reactions, with dissociation of the peptide in the first step. As shown by X-ray crystallography, only subtle structural differences between the subtypes were observed regarding the architecture of their F pockets, including the presence of distinct networks of water molecules. However, no consistent structural differences were found between the peptide presentation modes. In contrast to other peptides displayed by the two HLA-subtypes which show either structural or dynamical differences in their peptide presentation modes, the TIS-complexed HLA-B*2705 and HLA-B*2709 subtypes are an example for thermodynamic and structural equivalence, in agreement with functional data.

Binding Sites↗

PubMed2004

The solvent-inaccessible Cys67 residue of HLA-B27 contributes to T cell recognition of HLA-B27/peptide complexes.

Crystallographic studies have suggested that the cysteine at position 67 (Cys(67)) in the B pocket of the MHC molecule HLA-B*2705 is of importance for peptide binding, and biophysical studies have documented altered thermodynamic stability of the molecule when Cys(67) was mutated to serine (Ser(67)). In this study, we used HLA-B27.Cys(67) and HLA-B27.Ser(67) tetramers with defined T cell epitopes to determine the contribution of this polymorphic, solvent-inaccessible MHC residue to T cell recognition. We generated these HLA-B27 tetramers using immunodominant viral peptides with high binding affinity to HLA-B27 and cartilage-derived peptides with lower affinity. We demonstrate that the yield of refolding of HLA-B27.Ser(67) molecules was higher than for HLA-B27.Cys(67) molecules and strongly dependent on the affinity of the peptide. T cell recognition did not differ between HLA-B27.Cys(67) and HLA.B27.Ser(67) tetramers for the viral peptides that were investigated. However, an aggrecan peptide-specific T cell line derived from an HLA-B27 transgenic BALB/c mouse bound significantly stronger to the HLA-B27.Cys(67) tetramer than to the HLA-B27.Ser(67) tetramer. Modeling studies of the molecular structure suggest the loss of a SH ... pi hydrogen bond with the Cys-->Ser substitution in the HLA-B27 H chain which reduces the stability of the HLA-B27/peptide complex. These results demonstrate that a solvent-inaccessible residue in the B pocket of HLA-B27 can affect TCR binding in a peptide-dependent fashion.

Aggrecans↗

PubMed2004

Allele-dependent similarity between viral and self-peptide presentation by HLA-B27 subtypes.

Molecular mimicry is discussed as a possible mechanism that may contribute to the development of autoimmune diseases. It could also be involved in the differential association of the human major histocompatibility subtypes HLA-B(*)2705 and HLA-B(*)2709 with ankylosing spondylitis. These two subtypes differ only in residue 116 of the heavy chain (Asp in B(*)2705 and His in B(*)2709), but the reason for the differential disease association is not understood. Using x-ray crystallography, we show here that the viral peptide pLMP2 (RRRWRRLTV, derived from latent membrane protein 2 (residues 236-244) of Epstein-Barr virus) is presented by the B(*)2705 and B(*)2709 molecules in two drastically deviating conformations. Extensive structural similarity between pLMP2 and the self-peptide pVIPR (RRKWRRWHL, derived from vasoactive intestinal peptide type 1 receptor (residues 400-408)) is observed only when the peptides are presented by B(*)2705 because of a salt bridge between Arg(5) of both peptides and the subtype-specific heavy chain residue Asp(116). Combined with functional studies using pLMP2/pVIPR-cross-reactive cytotoxic T cell lines and clones, together with target cells presenting these peptides or a modified peptide analogue, our results reveal that a pathogen-derived peptide can exhibit major histocompatibility complex class I subtype-dependent, drastically distinct binding modes. Furthermore, the results demonstrate that molecular mimicry between pLMP2 and pVIPR in the HLA-B27 context is an allele-dependent property.

Alleles↗

PubMed2004

A major histocompatibility complex-peptide-restricted antibody and t cell receptor molecules recognize their target by distinct binding modes: crystal structure of human leukocyte antigen (HLA)-A1-MAGE-A1 in complex with FAB-HYB3.

Antibodies with T cell receptor-like specificity possess a considerable diagnostic and therapeutic potential, but the structural basis of the interaction between an antibody and an histocompatibility antigen has so far not been determined. We present here the crystal structure (at 2.15 A resolution) of the recombinant, affinity-matured human antibody fragment Fab-Hyb3 bound to the tumor-associated human leukocyte antigen (HLA)/peptide complex HLA-A1.MAGE-A1. Fab-Hyb3 employs a diagonal docking mode resembling that of T cell receptors. However, other than these natural ligands, the antibody uses only four of its six complementarity-determining regions for direct interactions with the target. It recognizes the C-terminal half of the MAGE-A1 peptide, the HLA-A1 alpha1-helix, and N-terminal residues of the alpha2-helix, accompanied by a large tilting angle between the two types of molecules within the complex. Interestingly, only a single hydrogen bond between a peptide side chain and Fab-Hyb3 contributes to the interaction, but large buried surface areas with pronounced shape complementarity assure high affinity and specificity for MAGE-A1. The HLA-A1.MAGE-A1.antibody structure is discussed in comparison with those of natural ligands recognizing HLA.peptide complexes.

Amino Acid Sequence↗

PubMed2004

A single residue exchange between two HLA-B27 alleles triggers increased peptide flexibility.

For more than 30 years, human leukocyte antigen B27 (HLA-B27) has been known to be closely related to the autoimmune disease ankylosing spondylitis, yet little is known about the molecular mechanisms of pathogenesis. Crystal structures of two closely related, but differently disease-associated, subtypes (B*2705 and B*2709) also did not resolve this situation as they revealed the bound nonapeptide in essentially identical conformations. As the peptide is part of putative binding epitopes for the T cell receptor, we performed molecular dynamics simulations to gain deeper insight into the dynamic behaviour of HLA-B27 molecules. We find increased flexibility of the peptide in the binding groove of subtype B*2709 due to weaker interactions in the F pocket. Possible implications of this flexibility for T cell recognition and signalling are discussed.

Alleles↗

PubMed2004

Dual, HLA-B27 subtype-dependent conformation of a self-peptide.

The products of the human leukocyte antigen subtypes HLA-B*2705 and HLA-B*2709 differ only in residue 116 (Asp vs. His) within the peptide binding groove but are differentially associated with the autoimmune disease ankylosing spondylitis (AS); HLA-B*2705 occurs in AS-patients, whereas HLA-B*2709 does not. The subtypes also generate differential T cell repertoires as exemplified by distinct T cell responses against the self-peptide pVIPR (RRKWRRWHL). The crystal structures described here show that pVIPR binds in an unprecedented dual conformation only to HLA-B*2705 molecules. In one binding mode, peptide pArg5 forms a salt bridge to Asp116, connected with drastically different interactions between peptide and heavy chain, contrasting with the second, conventional conformation, which is exclusively found in the case of B*2709. These subtype-dependent differences in pVIPR binding link the emergence of dissimilar T cell repertoires in individuals with HLA-B*2705 or HLA-B*2709 to the buried Asp116/His116 polymorphism and provide novel insights into peptide presentation by major histocompatibility antigens.

Amino Acid Sequence↗

PubMed2003

Thermodynamic and structural analysis of peptide- and allele-dependent properties of two HLA-B27 subtypes exhibiting differential disease association.

Selected HLA-B27 subtypes are associated with spondyloarthropathies, but the underlying mechanism is not understood. To explain this association in molecular terms, a comparison of peptide-dependent dynamic and structural properties of the differentially disease-associated subtypes HLA-B*2705 and HLA-B*2709 was carried out. These molecules differ only by a single amino acid at the floor of the peptide binding groove. The thermostabilities of a series of HLA-B27 molecules complexed with nonameric and decameric peptides were determined and revealed substantial differences depending on the subtype as well as the residues at the termini of the peptides. In addition we present the crystal structure of the B*2709 subtype complexed with a decameric peptide. This structure provides an explanation for the preference of HLA-B27 for a peptide with an N-terminal arginine as secondary anchor and the lack of preference for tyrosine as peptide C terminus in B*2709. The data show that differences in thermodynamic properties between peptide-complexed HLA-B27 subtypes are correlated with a variety of structural properties.

Amino Acid Sequence↗

PubMed2002

HLA-B27 subtypes differentially associated with disease exhibit subtle structural alterations.

The reasons for the association of the human major histocompatibility complex protein HLA-B27 with spondyloarthropathies are unknown. To uncover the underlying molecular causes, we determined the crystal structures of the disease-associated B*2705 and the nonassociated B*2709 subtypes complexed with the same nonapeptide (GRFAAAIAK). Both differ in only one residue (Asp(116) and His(116), respectively) in the F-pocket that accommodates the peptide C terminus. Several different effects of the Asp(116) --> His replacement are observed. The bulkier His(116) induces a movement of peptide C-terminal pLys(9), allowing the formation of a novel salt bridge to Asp(77), whereas the salt bridge between pLys(9) and Asp(116) is converted into a hydrogen bond with His(116). His(116) but not Asp(116) adopts two alternative conformations, one of which leads to breakage of hydrogen bonds. Water molecules near residue 116 differ with regard to number, position, and contacts made. Furthermore, F-pocket atoms exhibit higher B-factors in B*2709 than in B*2705, indicating an increased flexibility of the entire region in the former subtype. These changes induce subtle peptide conformational alterations that may be responsible for the immunobiological differences between these HLA-B27 subtypes.

Aspartic Acid↗

PubMedDate not supplied

Human CD30: structural implications from epitope mapping and modeling studies.

The human CD30 molecule is expressed transiently at very low levels on intrafollicular and perifollicular T and B cell blasts in lymphoid tissues, but is specifically upregulated on certain tumor cells, e.g. Hodgkin and Reed-Sternberg (H-RS) cells. With its specific expression pattern and easy accessibility on the surface of H-RS cells CD30 is a valuable diagnostic marker and holds considerable promise as a target for in vivo immunotherapy. Knowledge of epitopes on the CD30 molecule is expected to facilitate the design of novel non-immunogenic anti-CD30 reagents. Therefore, we have mapped the epitopes of several monoclonal antibodies (mAb) applying a peptide array of overlapping CD30-derived peptides. For the mAb Ber-H2, two linear epitopes with identical sequence were found, while the mAb Ki-2 and the single chain Fv fragment R4-4 each recognized a single linear antigenic determinant, respectively. On the other hand, the mAb Ki-1 bound to a discontinuous epitope composed of two regions, one located near the N-terminus and the other near the membrane-spanning region of CD30. Using molecular modeling, it was possible to visualize the location of the epitopes on exposed loop regions of the molecule within the N-terminal domain. Finally, the results obtained with the mAb Ki-1 imply that the ends of the N- and C-terminal parts of the extracellular portion of CD30 are in close vicinity of each other, suggesting a flower-like structure for the membrane-bound homotrimeric CD30 molecule.

Alanine↗