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From Proteopedia
CRYSTAL STRUCTURE OF RAT ALPHA 1-MACROGLOBULIN RECEPTOR BINDING DOMAIN
Structural highlights
Function[A1M_RAT] Is able to inhibit all four classes of proteinases by a unique 'trapping' mechanism. This protein has a peptide stretch, called the 'bait region' which contains specific cleavage sites for different proteinases. When a proteinase cleaves the bait region, a conformational change is induced in the protein which traps the proteinase. The entrapped enzyme remains active against low molecular weight substrates (activity against high molecular weight substrates is greatly reduced). Following cleavage in the bait region a thioester bond is hydrolyzed and mediates the covalent binding of the protein to the proteinase (By similarity).[UniProtKB:P01023] 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 PubMedAlpha-macroglobulin inhibits a broad spectrum of proteinases by forming macromolecular cages inside which proteinases are cross-linked and trapped. Upon formation of a complex with proteinase, alpha-macroglobulin undergoes a large conformational change that results in the exposure of its receptor-binding domain (RBD). Engagement of this domain by alpha-macroglobulin receptor permits clearance of the alpha-macroglobulin: proteinase complex from circulation. The crystal structure of rat alpha1-macroglobulin RBD has been determined at 2.3 A resolution. The RBD is composed of a nine-stranded beta-sandwich and a single alpha-helix that has been implicated as part of the receptor binding site and that lies on the surface of the beta-sandwich. The crystallographic asymmetric unit contains a dimer of RBDs related by approximate twofold symmetry such that the putative receptor recognition sites of the two monomers are contiguous. By gel filtration and ultracentrifugation, it is shown that RBD dimers form in solution with a dissociation constant of approximately 50 microM. The structure of the RBD dimer might mimic a conformation of transformed alpha-macroglobulin in which the proposed receptor binding residues are exposed on one face of the dimer. A pair of phenylalanine residues replaces a cystine that is conserved in other members of the macroglobulin family. These residues participate in a network of aromatic side-chain interactions that appears to stabilize the dimer interface. Structure of a rat alpha 1-macroglobulin receptor-binding domain dimer.,Xiao T, DeCamp DL, Spran SR Protein Sci. 2000 Oct;9(10):1889-97. PMID:11106161[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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