1ixu
From Proteopedia
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Solution structure of marinostatin, a protease inhibitor, containing two ester linkages
Overview
Marinostatin is a unique protein protease inhibitor containing two ester, linkages. We have purified a 12-residue marinostatin [MST(1-12), (1)FATMRYPSDSDE(12)] and determined the residues involved in the formation, of the ester linkages and the solution structure by (1)H NMR spectroscopy, and restrained molecular dynamics calculation. The two ester linkages of, MST(1-12) are formed between hydroxyl and carboxyl groups, Thr(3)-Asp(9), and Ser(8)-Asp(11), indicating that MST(1-12) has two cyclic regions which, are fused at the residues of Ser(8) and Asp(9). A strong NOE cross-peak, between Tyr(6) H(alpha) and Pro(7) H(alpha) was observed, indicating that, the Pro(7) residue takes a cis-conformation. Well-converged structures and, hydrogen-deuterium experiments of MST(1-12) showed that the backbone NH, proton of the P1'residue, Arg(5), is hydrogen-bonded to the carbonyl, oxygen of the ester linkage between Thr(3) and Asp(9). To reveal the, significance of the ester linkages, a marinostatin analogue, MST-2SS, ((1)FACMRYPCCSCE(12)) with two disulfide bridges of Cys(3)-Cys(9) and, Cys(8)-Cys(11), was also synthesized. The inhibitory activity of MST-2SS, was as strong as that of MST(1-12), and the Pro(7) residue of MST-2SS also, takes a cis-conformation. However, the exchange rate of the Arg(5) NH, proton of MST-2SS was about 100 times faster than that of MST(1-12), and, the structure calculation of MST-2SS was not converged on account of the, small number of NOEs, indicating that MST-2SS takes a more flexible, structure. The hydrogen acceptability of the ester linkage formed by the, P2 position residue, Thr(3), is crucial for suppressing the fluctuation of, the reactive site and sustaining the inhibitory activity, which enables, marinostatin to be one of the smallest protease inhibitors in nature.
About this Structure
1IXU is a Single protein structure of sequence from Alteromonas sp.. Full crystallographic information is available from OCA.
Reference
Solution structure of marinostatin, a natural ester-linked protein protease inhibitor., Kanaori K, Kamei K, Taniguchi M, Koyama T, Yasui T, Takano R, Imada C, Tajima K, Hara S, Biochemistry. 2005 Feb 22;44(7):2462-8. PMID:15709758
Page seeded by OCA on Tue Nov 20 17:45:38 2007
