1mce | pdb_00001mce
PRINCIPLES AND PITFALLS IN DESIGNING SITE DIRECTED PEPTIDE LIGANDS
Structural highlights
FunctionIGL1_HUMAN Immunoglobulins, also known as antibodies, are membrane-bound or secreted glycoproteins produced by B lymphocytes. In the recognition phase of humoral immunity, the membrane-bound immunoglobulins serve as receptors which, upon binding of a specific antigen, trigger the clonal expansion and differentiation of B lymphocytes into immunoglobulins-secreting plasma cells. Secreted immunoglobulins mediate the effector phase of humoral immunity, which results in the elimination of bound antigens (PubMed:22158414, PubMed:20176268). The antigen binding site is formed by the variable domain of one heavy chain, together with that of its associated light chain. Thus, each immunoglobulin has two antigen binding sites with remarkable affinity for a particular antigen. The variable domains are assembled by a process called V-(D)-J rearrangement and can then be subjected to somatic hypermutations which, after exposure to antigen and selection, allow affinity maturation for a particular antigen (PubMed:20176268, PubMed:17576170).[1] [2] [3] Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedAn immunoglobulin light chain dimer with a large generic binding cavity was used as a host molecule for designing a series of peptide guest ligands. In a screening procedure peptides coupled to solid supports were systematically tested for binding activity by enzyme linked immunosorbent assays (ELISA). Key members of the binding series were synthesized in milligram quantities and diffused into crystals of the host molecule for X-ray analyses. These peptides were incrementally increased in size and affinity until they nearly filled the cavity. Progressive changes in binding patterns were mapped by comparisons of crystallographically refined structures of 14 peptide-protein complexes at 2.7 A resolution. These comparisons led to guidelines for ligand design and also suggested ways to modify previously established binding patterns. By manipulating equilibria involving histidine, for example, it was possible to abolish one important intramolecular interaction of the bound ligand and substitute another. These events triggered a change in conformation of the ligand from a compact to an extended form and a comprehensive change in the mode of binding to the protein. In dipeptides of histidine and proline, protonation of both imidazolium nitrogen atoms was used to program an end-to-end reversal of the direction in which the ligand was inserted into the binding cavity. Peptides cocrystallized with proteins produced complexes somewhat different in structure from those in which ligands were diffused into preexisting crystals. In such a large and malleable cavity, space utilization was thus different when a ligand was introduced before the imposition of crystal packing restraints. Principles and pitfalls in designing site-directed peptide ligands.,Edmundson AB, Harris DL, Fan ZC, Guddat LW, Schley BT, Hanson BL, Tribbick G, Geysen HM Proteins. 1993 Jul;16(3):246-67. PMID:8346191[4] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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