1pj8

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spinqualitylabelsall models 1pj8, resolution 2.2Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image

Structure of a ternary complex of proteinase K, mercury and a substrate-analogue hexapeptide at 2.2 A resolution

Overview

The crystal structure of a ternary complex of proteinase K, Hg(II) and a, hexapeptide N-Ac-Pro-Ala-Pro-Phe-Pro-Ala-NH2 has been determined at 2.2 A, resolution and refined to an R factor of 0.172 for 12,910 reflections. The, mercury atom occupies two alternate sites, each of which was assigned an, occupancy of 0.45. These two sites are bridged by Cys-73 S gamma which, forms covalent bonds to both. Both mercury sites form regular polyhedrons, involving atoms from residues Asp-39, His-69, Cys-73, His-72, Met-225, and, Wat-324. The complex formation with mercury seems to disturb the, stereochemistry of the residues of the catalytic triad Asp-39, His-69, and, Ser-224 appreciably, thus reducing the enzymatic activity of proteinase K, to 15%. The electron density in the difference Fourier map shows that the, hexapeptide occupies the S1 subsite predominantly and the standard, recognition site constituted by Ser-132 to Gly-136 and Gly-100 to Tyr-104, segments is virtually empty. The hexapeptide is held firmly through a, series of hydrogen bonds involving protein atoms and water molecules. As a, result of complex formation, Asp-39, His-69, Met-225, Ile-220, Ser-219, Thr-223, and Ser-224 residues move appreciably to accommodate the mercury, atoms and the hexapeptide. The largest movement is observed for Met-225, which is involved in multiple interactions with both mercury and the, hexapeptide. The activity results indicate an inhibition rate of 95%, as a, result of the combined effect of mercury and hexapeptide.

About this Structure

1PJ8 is a Single protein structure of sequence from Engyodontium album with HG and NH2 as ligands. Active as Peptidase K, with EC number 3.4.21.64 Full crystallographic information is available from OCA.

Reference

Structure of a ternary complex of proteinase K, mercury, and a substrate-analogue hexa-peptide at 2.2 A resolution., Saxena AK, Singh TP, Peters K, Fittkau S, Visanji M, Wilson KS, Betzel C, Proteins. 1996 Jun;25(2):195-201. PMID:8811735

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