YihI activates the GTPase activity of Der, a 50S ribosomal subunit stability factor [1]. The stimulation is specific to Der as YihI does not stimulate the GTPase activity of Era or ObgE. The interaction of YihI with Der requires only the C-terminal 78 amino acids of YihI [1]. A yihI deletion mutant is viable and shows a shorter lag period, but the same post-lag growth rate as a wild-type strain. yihI is expressed during the lag period. Overexpression of yihI inhibits cell growth and biogenesis of the 50S ribosomal subunit [1]. YihI is an unusual, highly hydrophilic protein with an uneven distribution of charged residues, resulting in an N-terminal region with high pI and a C-terminal region with low pI [1].

1: A bacterial GAP-like protein, YihI, regulating the GTPase of Der, an essential GTP-binding protein in Escherichia coli. Hwang J, Inouye M; J Mol Biol. 2010;399:759-772. PMID:20434458