The biosynthesis of the thiazole phosphate moiety of thiamin: the sulfur transfer mediated by the sulfur carrier protein ThiS.
Thiamin-pyrophosphate is an essential cofactor in all living systems. The biosynthesis of both the thiazole and the pyrimidine moieties of this cofactor involves new biosynthetic chemistry. Thiazole-phosphate synthase (ThiG) catalyses the formation of the thiazole moiety of thiamin-pyrophosphate from 1-deoxy-D-xylulose-5-phosphate (DXP), dehydroglycine and the sulfur carrier protein (ThiS), modified on its carboxy terminus as a thiocarboxylate (ThiS-thiocarboxylate). Thiazole biosynthesis is initiated by the formation of a ThiG/DXP imine, which then tautomerizes to an amino-ketone. In this paper we study the sulfur transfer from ThiS-thiocarboxylate to this amino-ketone and trap a new thioenolate intermediate. Surprisingly, thiazole formation results in the replacement of the ThiS-thiocarboxylate sulfur with an oxygen from DXP and not from the buffer, as shown by electrospray ionization Fourier transform mass spectrometry (ESI-FTMS) using (18)O labeling of the 13C-, 15N-depleted protein. These observations further clarify the mechanism of the complex thiazole biosynthesis in bacteria.
Dorrestein
Pieter C
PC
Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853, USA.
Zhai
Huili
H
McLafferty
Fred W
FW
Begley
Tadhg P
TP
D000595:Amino Acid Sequence; D001412:Bacillus subtilis / Q000201:enzymology*; D002352:Carrier Proteins / Q000096:biosynthesis*; D002384:Catalysis; D029968:Escherichia coli Proteins / Q000096:biosynthesis; D008969:Molecular Sequence Data; D010428:Pentosephosphates / Q000096:biosynthesis*; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods; D013457:Sulfur Compounds / Q000032:analysis / Q000138:chemical synthesis*; D013831:Thiamine / Q000096:biosynthesis* / Q000737:chemistry*; D013838:Thiamine Triphosphate / Q000138:chemical synthesis / Q000378:metabolism; D013844:Thiazoles / Q000737:chemistry* / Q000378:metabolism*; D014166:Transferases / Q000737:chemistry / Q000378:metabolism
C109460:1-deoxylulose 5-phosphate; D002352:Carrier Proteins; D029968:Escherichia coli Proteins; D010428:Pentosephosphates; D013457:Sulfur Compounds; D013844:Thiazoles; C411655:thiS protein, E coli; D013838:Thiamine Triphosphate; D014166:Transferases; C109461:deoxyxylulose-5-phosphate synthase; D013831:Thiamine