2C3Z

Crystal structure of a truncated variant of indole-3-glycerol phosphate synthase from Sulfolobus solfataricus

Summary for 2C3Z

• Entry DOI: 10.2210/pdb2c3z/pdb
• Related: 1A53 1IGS 1JUK 1JUL 1LBF 1LBL
• Descriptor: INDOLE-3-GLYCEROL PHOSPHATE SYNTHASE, SULFATE ION (3 entities in total)
• Functional Keywords: indole-3-glycerol phosphate synthase, protein stability, catalytic activity, divergent evolution, tryptophan biosynthesis, lyase, decarboxylase
• Biological source: SULFOLOBUS SOLFATARICUS
• Total number of polymer chains: 1
• Total formula weight: 25572.37

Authors

Schneider, A.,Knoechel, T.,Darimont, B.,Hennig, M.,Dietrich, S.,Kirschner, K.,Sterner, R. (deposition date: 2005-10-13, release date: 2005-10-13, Last modification date: 2023-12-13)

Primary citation

Schneider, B.,Knoechel, T.,Darimont, B.,Hennig, M.,Dietrich, S.,Babinger, K.,Kirschner, K.,Sterner, R.
Role of the N-Terminal Extension of the (Betaalpha)(8)-Barrel Enzyme Indole-3-Glycerol Phosphate Synthase for its Fold, Stability, and Catalytic Activity.
Biochemistry, 44:16405-, 2005

PubMed Abstract: 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.

PubMed: 16342933
DOI: 10.1021/BI051640N

Experimental method

X-RAY DIFFRACTION (2.8 Å)