The Role of the YjeQ GTPase in Bacterial Ribosome Biogenesis: Function of the C-terminal Zinc-finger Domain

Abstract

<p>Our understanding of the mechanism of ribosome assembly in bacteria is still in its infancy. Work from our laboratory and others have recently established that some protein assembly factors assist the assembly process at its late stages, mediating the correct folding of the functional core of the 30S and 50S subunits. The GTPase YjeQ is an assembly factor that displaces the upper domain of h44 of the mature 30S subunit upon binding, inducing a distortion in the decoding center. We hypothesized that the displacement of h44 is caused by the zinc-finger domain of YjeQ and mediates the release of RbfA, another assembly factor involved in 30S subunit maturation. To understand how the zinc-finger domain of YjeQ implements the functional interplay with RbfA, we constructed several deletion mutants of the domain. We found that the zinc-finger domain of YjeQ was required to bind the 30S subunit, but not the C-terminal extension (CTE) of the domain. The CTE was necessary for stimulation of GTPase activity upon binding to the 30S subunit and removal of bound RbfA from the 30S subunit. The data presented here suggests that the zinc-finger domain is essential for YjeQ to bind the 30S subunit and to implement the functional interplay with RbfA. Ongoing structural studies of the complex formed by the YjeQ CTE variant and the 30S subunit will provide a three dimensional view of the conformational changes that occur to implement the functional interplay between YjeQ and RbfA at the late stages of 30S subunit assembly.</p>