3tec

From Proteopedia

proteopedia linkproteopedia link

spinqualitylabelsall models 3tec, resolution 2.0Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image

CALCIUM BINDING TO THERMITASE. CRYSTALLOGRAPHIC STUDIES OF THERMITASE AT 0, 5 AND 100 MM CALCIUM

Overview

The three-dimensional crystal structure of thermitase complexed with, eglin-c in the presence of 100 mM calcium has been determined and refined, at 2.0-A resolution to a R-factor of 16.8%. This crystal structure is, compared with previously determined structures of thermitase at 0 and 5 mM, calcium concentration. In the presence of 100 mM calcium all three calcium, binding sites in thermitase are fully occupied. At 100 mM CaCl2 the "weak", calcium binding is occupied by a calcium ion, which is chelated by three, protein ligands and four water molecules in a pentagonal bipyramid, geometry. Thermitase has, apparently, a monovalent and divalent cation, binding position at 2.5-A distance from each other at this site. At low, calcium concentrations the monovalent-ion position is occupied by a sodium, or potassium ion. The "medium strength" binding site shows in the presence, of 100 mM CaCl2 a square antiprism arrangement with eight ligands, of, which seven are donated by the protein. At low calcium concentrations we, observe a distorted pentagonal bipyramid coordination at this site. The, largest difference between these two conformations is observed for ligand, Asp-60, which has two conformations with 0.8-A difference in C alpha, positions. The "strong" calcium binding site has a pentagonal bipyramid, coordination and is fully occupied in all three structures. Structural, changes on binding calcium to the weak and "medium strength" calcium, binding sites of thermitase are limited to the direct surroundings of, these sites. Thermitase resembles in this respect subtilisin BPN' and does, not exhibit long-range shifts as have been reported for proteinase K.

About this Structure

3TEC is a Protein complex structure of sequences from Hirudinaria manillensis and Thermoactinomyces vulgaris with CA as ligand. Active as Thermitase, with EC number 3.4.21.66 Full crystallographic information is available from OCA.

Reference

Calcium binding to thermitase. Crystallographic studies of thermitase at 0, 5, and 100 mM calcium., Gros P, Kalk KH, Hol WG, J Biol Chem. 1991 Feb 15;266(5):2953-61. PMID:1993669

Page seeded by OCA on Tue Nov 20 19:59:22 2007