Steve Ealick's Research Group

Thiazole Synthase/Sulfur Carrier Protein Complex (ThiSG)

PDB file:



Thiamin pyrophosphate is an essential cofactor in all living systems and consists of a pyrimidine covalently linked to a thiazole. The thiazole moiety is biosynthesized in Bacillus subtilis from 1-deoxy-D-xylulose-5-phosphate, glycine and cysteine in a complex oxidative condensation reaction requiring five different proteins. Of these ThiS is the sulfur carrier protein and carries the sulfur needed for thiazole assembly on its carboxy terminus (ThiS-COSH). ThiG is the thiazole synthase and catalyzes the formation of the thiazole from DXP, ThiS-COSH and dehydroglycine.

The ThiS/thiazole synthase heterodimer consists of ThiS, a 7.2 kDa protein with a ubiquitin-like fold, and thiazole synthase, a 26.9 kDa protein.


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In the crystal structure thiazole synthase, complexed with the sulfur carrier protein, consists of a tetramer of ThiS/thiazole synthase heterodimers.


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In this drawing of the putative active site, thiazole synthase is shown as a surface representation and ThiS is shown as a blue coil. Conserved residues with predicted functions are shown: Lys96 (blue), Glu98 (red) and Asp182 (yellow). Conserved residues without an assigned function are colored green while an exposed hydrophobic surface is shown in cyan. The red ball-and-stick figures represent phosphate ions.

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Settembre EC, Dorrestein PC, Zhai H, Chatterjee A, McLafferty FW, Begley TP, and Ealick SE. Thiamin Biosynthesis in Bacillus subtilis: Structure of the Thiazole Synthase/Sulfur Carrier Protein Complex, Biochemistry 43:11647-11657 (2004).

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