The GTP-binding protein YqeH participates in biogenesis of the 30S ribosome subunit in Bacillus subtilis

Abstract

Bacterial genome sequencing has revealed a novel family of P-loop GTPases that are often essential for growth. Accumulating evidence suggests that these proteins are involved in biogenesis of the 30S or 50S ribosomal subunits. YqeH is a member of this Obg/Era GTPase family, with its function remains to be uncovered. Here, we present results showing that YqeH is involved in the 30S subunit biogenesis in Bacillus subtilis. We observed a reduction in the 70S ribosome and accumulation of the free 50S subunit in YqeH-depleted cells. Interestingly, no free 30S subunit accumulation was evident. Consistent with the theory that YqeH is involved in 30S subunit biogenesis, a precursor of 16S rRNA and its degradation products were detected. Additionally, the reduction of free 30S subunit was not observed in Eradepleted cells. YqeH overexpression did not compensate for growth defects in mutants devoid of Era and vice versa. Moreover, in vitro GTPase analyses showed that YqeH possessed high intrinsic GTPase activity. In contrast, Era showed slow GTPase activity, which was enhanced by the 30S ribosomal subunit. Our findings strongly suggest that YqeH and Era function at distinct checkpoints during 30S subunit assembly. B. subtilis yqeH is classified as an essential gene due to the inability of the IPTG-dependent P spac -yqeH mutant to grow on LB or PAB agar plates in the absence of IPTG. However, in our experiments, the P spac -yqeH mutant grew in PAB liquid medium without IPTG supplementation, albeit at an impaired rate. This finding raises the interesting possibility that YqeH participates in assembly of the 30S ribosomal subunit as well as other cellular functions essential for growth on solid media.

The Structure of YqeH

“…Both YlqF and YqeH are essential for cell growth in Bacillus subtilis. They have been shown to bind [␣- 32 P]GTP (31), and GTPase activity was demonstrated for YqeH (32). The B. subtilis yqeH mutant is lethal, whereas reduced YqeH expression increases chromosomal replication (31).…”

“…The B. subtilis yqeH mutant is lethal, whereas reduced YqeH expression increases chromosomal replication (31). YqeH participates in the biogenesis of the 30 S ribosome subunit (32) and assists in 50 S ribosome assembly (33). A high throughput screen in yeast found that a distant homolog of YqeH interacts with a ribosomal protein (31,34,35).…”

The Putative GTPase Encoded by MTG3 Functions in a Novel Pathway for Regulating Assembly of the Small Subunit of Yeast Mitochondrial Ribosomes

“…Gradients-The deficit of the 15 S rRNA in the mtg3 ts mutant grown under restrictive conditions and previous evidence implicating the YqeH GTPase of Bacillus subtilis in assembly of the 30 S ribosomal subunit (29,30) suggested that Mtg3p might play a similar role in yeast mitochondria. This was also consistent with detection of normal sedimenting 54 S subunit in the different mtg3 mutants examined.…”

“…Although mtg3 null and ts mutants grown at the nonpermissive temperature displayed a reduction in the 54 S subunit, this is related to the high percentage of o/Ϫ cells in the strains. Last, YqeH, an Mtg3p homologue of B. subtilis has also been implicated in assembly of the 30 S but not the 50 S ribosomal subunit of this organism (29,30). The bacterial protein has been shown to bind to 30 S subunit (45) but its function in assembly has yet to be elucidated.…”

Removal of a ribosome small subunit-dependent GTPase confers salt resistance on Escherichia coli cells

“…Its maturation involves cleavage and trimming of the precursors of rRNA, modification of the base or ribose of rRNA, assembly of ribosomal proteins, and proper folding (Lu and Inouye 1998;Kaczanowska and Rydén-Aulin 2007;Wilson and Nierhaus 2007). These processes require the help of a considerable number of trans-acting factors in the cell (Jones and Inouye 1996;Bylund et al 1998;Inoue et al 2003;Kaczanowska and Rydén-Aulin 2004;Sato et al 2005;Karbstein 2007;Loh et al 2007), although a functional ribosomal particle can be reconstituted from the components in vitro without any trans-acting factors (Held et al 1974;Holmes and Culver 2005).…”