Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.2.1.17 (lysozyme)
 21,489 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The Camelidae is the only taxonomic family known to possess functional heavy-chain antibodies, lacking light chains. We report here the 2.5 A resolution crystal structure of a camel VH in complex with its antigen, lysozyme. Compared to human and mouse VH domains, there are no major backbone rearrangements in the VH framework. However, the architecture of the region of VH that interacts with a VL in a conventional FV is different from any previously seen. Moreover, the CDR1 region, although in sequence homologous to human CDR1, deviates fundamentally from the canonical structure. Additionally, one half of the CDR3 contacts the VH region which in conventional immunoglobulins interacts with a VL whereas the other half protrudes from the antigen binding site and penetrates deeply into the active site of lysozyme.
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PMID:Crystal structure of a camel single-domain VH antibody fragment in complex with lysozyme. 878 42

Naturally processed MHC class II-bound peptides possess ragged NH2 and COOH termini. It is not known whether these peptide flanking residues (PFRs), which lie outside the MHC anchor residues, are recognized by the TCR or influence immunogenicity. Here we analyzed T cell responses to the COOH-terminal PFR of the H-2A(k) immunodominant epitope of hen egg lysozyme (HEL) 52-61. Surprisingly, the majority of T cells were completely dependent on, and specific for, the COOH-terminal PFR of the immunogen. In addition, there were striking correlations between TCR V beta usage and PFR dependence. We hypothesize that the V alpha CDR1 region recognizes NH2-terminal PFRs, while the V beta CDR1 region recognizes COOH-terminal PFRs. Last, peptides containing PFRs were considerably more immunogenic and mediated a greater recall response to the HEL protein. These results demonstrate that PFRs, which are a unique characteristic of peptides bound to MHC class II molecules, can have a profound effect on TCR recognition and T cell function. These data may have important implications for peptide-based immunotherapy and vaccine development.
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PMID:T cell receptor recognition of MHC class II-bound peptide flanking residues enhances immunogenicity and results in altered TCR V region usage. 932 59

Neocarzinostatin (NCS) is a small "all beta" protein displaying the same overall fold as immunoglobulins. This protein possesses a well-defined hydrophobic core and two loops structurally equivalent to the CDR1 and CDR3 of immunoglobulins. NCS is the most studied member of the enediynechromoprotein family, and is clinically used as an antitumoral agent. NCS has promise as a drug delivery vehicle if new binding specificities could be conferred on its protein scaffold. Previous studies have shown that the binding specificity of the crevasse can be extended to compounds completely unrelated to the natural enediyne chromophore family. We show here that it is possible to introduce new interaction capacities to obtain a protein useful for drug targeting by modifying the immunoglobulin CDR-like loops. We transferred the CDR3 of the VHH chain of camel antilysozyme immunoglobulin to the equivalent site in the corresponding loop of neocarzinostatin. We then evaluated the stability of the resulting structure and its affinity for lysozyme. The engineered NCS-CDR3 presents a structure similar to that of the wild-type NCS, and is stable and efficiently produced. ELISA, ITC, and SPR measurements demonstrated that the new NCS-CDR3 specifically bound lysozyme.
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PMID:Affinity transfer by CDR grafting on a nonimmunoglobulin scaffold. 1516 56

Affinity maturation of classic antibodies supposedly proceeds through the pre-organization of the reactive germ line conformational isomer. It is less evident to foresee how this can be accomplished by camelid heavy-chain antibodies lacking light chains. Although these antibodies are subjected to somatic hypermutation, their antigen-binding fragment consists of a single domain with restricted flexibility in favor of binding energy. An antigen-binding domain derived from a dromedary heavy-chain antibody, cAb-Lys3, accumulated five amino acid substitutions in CDR1 and CDR2 upon maturation against lysozyme. Three of these residues have hydrophobic side chains, replacing serines, and participate in the hydrophobic core of the CDR1 in the mature antibody, suggesting that conformational rearrangements might occur in this loop during maturation. However, transition state analysis of the binding kinetics of mature cAb-Lys3 and germ line variants show that the maturation of this antibody relies on events late in the reaction pathway. This is reflected by a limited perturbation of k(a) and a significantly decreased k(d) upon maturation. In addition, binding reactions and the maturation event are predominantly enthalpically driven. Therefore, maturation proceeds through the increase of favorable binding interactions, or by the reduction of the enthalpic penalty for desolvation, as opposed to large entropic penalties associated with conformational changes and structural plasticity. Furthermore, the crystal structure of the mutant with a restored germ line CDR2 sequence illustrates that the matured hydrophobic core of CDR1 in cAb-Lys3 might be compensated in the germ line precursor by burying solvent molecules engaged in a stable hydrogen-bonding network with CDR1 and CDR2.
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PMID:Chemical basis for the affinity maturation of a camel single domain antibody. 1538 40