2ovd
From Proteopedia
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Crystal Structure of Human Complement Protein C8gamma with Laurate
Overview
Human C8 is one of five components of the cytolytic membrane attack, complex of complement. It contains three subunits (C8alpha, C8beta, C8gamma) arranged as a disulfide-linked C8alpha-gamma heterodimer that is, noncovalently associated with C8beta. C8gamma has the distinction of being, the only lipocalin in the complement system. Lipocalins have a core, beta-barrel structure forming a calyx with a binding site for a small, hydrophobic ligand. A natural ligand for C8gamma has not been identified;, however previous structural studies indicate C8gamma has a typical, lipocalin fold that is suggestive of a ligand-binding capability. A, distinctive feature of C8gamma is the division of its putative ligand, binding pocket into a hydrophilic upper portion and a large hydrophobic, lower cavity. Access to the latter is restricted by the close proximity of, two tyrosine side chains (Y83 and Y131). In the present study, binding, experiments were performed using lauric acid as a pseudoligand to, investigate the potential accessibility of the lower cavity. The crystal, structure of a C8gamma.laurate complex revealed that Y83 and Y131 can move, to allow penetration of the hydrocarbon chain of laurate into the lower, cavity. Introducing a Y83W mutation blocked access but had no effect on, the ability of C8gamma to enhance C8 cytolytic activity. Together, these, results indicate that the lower cavity in C8gamma could accommodate a, ligand if such a ligand has a narrow hydrophobic moiety at one end. Entry, of that moiety into the lower cavity would require movement of Y83 and, Y131, which act as a gate at the cavity entrance.
About this Structure
2OVD is a Single protein structure of sequence from Homo sapiens with as ligand. Full crystallographic information is available from OCA.
Reference
Structural features of the ligand binding site on human complement protein C8gamma: A member of the lipocalin family., Chiswell B, Lovelace LL, Brannen C, Ortlund EA, Lebioda L, Sodetz JM, Biochim Biophys Acta. 2007 May;1774(5):637-44. Epub 2007 Mar 20. PMID:17452033
Page seeded by OCA on Wed Jan 23 15:12:49 2008
