YeiR: a metal-binding GTPase from Escherichia coli involved in metal homeostasis.

A comparative genomic analysis predicted that many members of the under-characterized COG0523 subfamily of putative P-loop GTPases function in metal metabolism. In this work we focused on the uncharacterized Escherichia coli protein YeiR by studying both the physiology of a yeiR mutant and the in vitro biochemical properties of YeiR expressed as a fusion with the maltose-binding protein (YeiR-MBP). Our results demonstrate that deletion of yeiR increases the sensitivity of E. coli to EDTA or cadmium, and this phenotype is linked to zinc depletion. In vitro, the tagged protein binds several Zn(2+) ions with nanomolar affinity and oligomerizes in the presence of metal. The GTPase activity of YeiR is similar to that measured for other members of the group, but GTP hydrolysis is enhanced by Zn(2+) binding. These results support the predicted connection between the COG0523 P-loop GTPases and roles in metal homeostasis.