Mutational analysis of YgfZ, a folate-dependent protein implicated in iron/sulphur cluster metabolism

Ghulam Hasnain, Jeffrey C. Waller, Sophie Alvarez, Geoffrey E. Ravilious, Joseph M. Jez, Andrew D. Hanson

Research output: Contribution to journalArticlepeer-review

9 Scopus citations


Proteins of the YgfZ family occur in all domains of life and are characterized by the conserved dodecapeptide motif KGC[Y/F]-x-GQE-x 3-[R/K]. YgfZ proteins are known to participate in assembly or repair of iron/sulphur clusters, and to require folate for biological activity, but their mechanism of action is unknown. To assess the importance of individual residues in the conserved motif, Escherichia coli Ygf Z was expressed from a plasmid in a ΔygfZ strain and subjected to alanine-scanning mutagenesis. The impacts on YgfZ functionality were evaluated by assays of growth and of the in vivo activity of the iron/sulphur enzyme MiaB, which modifies tRNA. By these criteria, the motif's tyrosine residue (Y229) had a detectable influence but only the cysteine residue (C228) was critical, for only the C228A mutant failed to complement the growth and MiaB activity phenotypes of the ΔygfZ strain. Immunoblots confirmed that the latter result was not simply because of a low level of the C228A mutant protein. Collectively, these data demonstrate a pivotal role for the Ygf Z motif's cysteine residue and a subsidiary one for the adjacent tyrosine, and help formulate a hypothesis about the folate requirement of Ygf Z proteins.

Original languageEnglish (US)
Pages (from-to)168-172
Number of pages5
JournalFEMS Microbiology Letters
Issue number2
StatePublished - Jan 2012
Externally publishedYes


  • Essential cysteine
  • Folate
  • Iron/sulphur proteins
  • MiaB
  • YgfZ

ASJC Scopus subject areas

  • General Medicine


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