2f9o
Crystal Structure of the Recombinant Human Alpha I Tryptase Mutant D216G
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OverviewOverview
Tryptases alpha and beta are trypsin-like serine proteinases expressed in, large amounts by mast cells. Beta-tryptase is a tetramer that has, enzymatic activity, but requires heparin binding to maintain functional, and structural stability, whereas alpha-tryptase has little, if any, enzymatic activity but is a stable tetramer in the absence of heparin. As, shown previously, these differences can be mainly attributed to the, different conformations of the 214-220 segment. Interestingly, the, replacement of Asp216 by Gly, which is present in beta-tryptase, results, in enzymatically active but less stable alpha-tryptase mutants. We have, solved the crystal structures of both the single (D216G) and the double, (K192Q/D216G) mutant forms of recombinant human alphaI-tryptase in complex, with the peptide inhibitor leupeptin, as well as the structure of the, non-inhibited single mutant. The inhibited mutants exhibited an open, functional substrate binding site, while in the absence of an inhibitor, the open (beta-tryptase-like) and the closed (alpha-tryptase-like), conformations were present simultaneously. This shows that both forms are, in a two-state equilibrium, which is influenced by the residues in the, vicinity of the active site and by inhibitor/substrate binding. Novel, insights regarding the observed stability differences as well as a, potential proteolytic activity of wild-type alpha-tryptase, which may, possess a cryptic active site, are discussed.
About this StructureAbout this Structure
2F9O is a Single protein structure of sequence from Homo sapiens. Active as Tryptase, with EC number 3.4.21.59 Full crystallographic information is available from OCA.
ReferenceReference
X-ray structures of free and leupeptin-complexed human alphaI-tryptase mutants: indication for an alpha-->beta-tryptase transition., Rohr KB, Selwood T, Marquardt U, Huber R, Schechter NM, Bode W, Than ME, J Mol Biol. 2006 Mar 17;357(1):195-209. Epub 2005 Dec 28. PMID:16414069
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