The Biosynthesis of the Thiazole Phosphate Moiety of Thiamin The Sulfur Transfer Mediated by the Sulfur Carrier Protein ThiS Academic Article uri icon

abstract

  • 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.

altmetric score

  • 3.5

author list (cited authors)

  • Dorrestein, P. C., Zhai, H., McLafferty, F. W., & Begley, T. P.

citation count

  • 23

publication date

  • October 2004