2c3z

From Proteopedia

Revision as of 08:31, 3 February 2008

CRYSTAL STRUCTURE OF A TRUNCATED VARIANT OF INDOLE-3-GLYCEROL PHOSPHATE SYNTHASE FROM SULFOLOBUS SOLFATARICUS

Overview

Indole-3-glycerol phosphate synthase (IGPS) catalyzes the fifth step in, the biosynthesis of tryptophan. It belongs to the large and versatile, family of (betaalpha)(8)-barrel enzymes but has an unusual N-terminal, extension of about 40 residues. Limited proteolysis with trypsin of IGPS, from both Sulfolobus solfataricus (sIGPS) and Thermotoga maritima (tIGPS), removes about 25 N-terminal residues and one of the two extra helices, contained therein. To assess the role of the extension, the N-terminally, truncated variants sIGPSDelta(1-26) and tIGPSDelta(1-25) were produced, recombinantly in Escherichia coli, purified, and characterized in, comparison to the wild-type enzymes. Both sIGPSDelta(1-26) and, tIGPSDelta(1-25) have unchanged oligomerization states and turnover, numbers. In contrast, their Michaelis constants for the substrate, 1-(o-carboxyphenylamino)-1-deoxyribulose 5-phosphate are increased, and, their resistance toward unfolding induced by heat and guanidinium chloride, is decreased. sIGPSDelta(1-26) was crystallized, and its X-ray structure, was solved at 2.8 A resolution. The comparison with the known structure of, sIGPS reveals small differences that account for its reduced substrate, affinity and protein stability. The structure of the core of, sIGPSDelta(1-26) is, however, unchanged compared to sIGPS, explaining its, retained catalytic activity and consistent with the idea that it evolved, from the same ancestor as the phosphoribosyl anthranilate isomerase and, the alpha-subunit of tryptophan synthase. These (betaalpha)(8)-barrel, enzymes catalyze the reactions preceding and following IGPS in tryptophan, biosynthesis but lack an N-terminal extension.

About this Structure

2C3Z is a Single protein structure of sequence from Sulfolobus solfataricus with as ligand. Active as Indole-3-glycerol-phosphate synthase, with EC number 4.1.1.48 Known structural/functional Site: . Full crystallographic information is available from OCA.

Reference

Role of the N-terminal extension of the (betaalpha)8-barrel enzyme indole-3-glycerol phosphate synthase for its fold, stability, and catalytic activity., Schneider B, Knochel T, Darimont B, Hennig M, Dietrich S, Babinger K, Kirschner K, Sterner R, Biochemistry. 2005 Dec 20;44(50):16405-12. PMID:16342933

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