Thiamine biosynthesis in Escherichia coli:: isolation and initial characterisation of the ThiGH complex

In Escherichia coli, two of the proteins required for the biosynthesis of the thiazole moiety of thiamine (vitamin B-1) are ThiG and ThiH, encoded as part of the thiCEFSGH operon. In this study, a C-terminally hexahistidine-tagged ThiH (ThiH-His) was expressed in E. coli as a soluble protein from thiGH-His-tag and thiFSGH-His-tag-bearing plasmids. When isolated under anaerobic conditions, ThiG and ThiH-His co-purify as a large multimeric non-covalent complex. Electron paramagnetic resonance and UV-visible spectroscopy together with iron and sulfide analyses revealed the presence of an iron-sulfur cluster within this complex. (C) 2003 Published by Elsevier Science B.V. on behalf of the Federation of European Biochemical Societies.