2tir

File:2tir.jpg

CRYSTAL STRUCTURE ANALYSIS OF A MUTANT ESCHERICHIA COLI THIOREDOXIN IN WHICH LYSINE 36 IS REPLACED BY GLUTAMIC ACID

Overview

The structure of a mutant Escherichia coli thioredoxin with a glutamic acid substituted for a conserved lysine at position 36 adjacent to the active site has been solved using molecular replacement and refined at 2.0-A resolution to a crystallographic residual of 19.9%. The mutant was crystallized in an orthorhombic space group with one molecule in the asymmetric unit. The structure of the mutant thioredoxin shows overall good agreement with the wild-type E. coli thioredoxin. The root-mean-square deviations for all C alpha s are 0.45 and 0.79 A between the mutant structure and the two molecules in the asymmetric unit of the wild-type crystals. Structural changes are seen in several residues in the active-site region preceding the disulfide. A reverse turn of residues 29-32 changes the conformation from a type I to a type II turn. This change may be related to the loss of a hydrogen bond from Lys-36 to the main-chain carbonyl of residue 30 due to the mutation. The C alpha atom of Trp-31 has moved 1.9 A and the indole ring no longer makes hydrogen bonds to the carboxyl group of Asp-61 but instead participates in a crystal contact. The structural differences seen in the mutant thioredoxin may be influenced by the crystal packing. The substituted Glu-36 makes extensive crystal contacts. The static fluorescence of this mutant thioredoxin has a different pH dependence than the wild type.

About this Structure

2TIR is a Single protein structure of sequence from Escherichia coli. Full crystallographic information is available from OCA.

Reference

Crystal structure analysis of a mutant Escherichia coli thioredoxin in which lysine 36 is replaced by glutamic acid., Nikkola M, Gleason FK, Fuchs JA, Eklund H, Biochemistry. 1993 May 18;32(19):5093-8. PMID:8098620 Page seeded by OCA on Sun May 4 17:24:13 2008

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