The function of RNase G in Escherichia coli is constrained by its amino and carboxyl termini.
RNase G is a homologue of the essential Escherichia coli ribonuclease RNase E. Whereas RNase E plays a key role in the degradation of mRNA and the processing of tRNA and rRNA in E. coli, the biological functions of RNase G appear more limited. We report here that this difference in function is not merely a consequence of the significantly lower cellular concentration of RNase G, but also reflects differences in the intrinsic properties of these ribonucleases, as overproducing wild-type RNase G at a level up to 20 times the usual cellular concentration of RNase E cannot normally compensate for the absence of RNase E in E. coli. Instead, RNase G can sustain significant growth of RNase E-deficient E. coli cells only when it bears an unnatural extension at its amino terminus (e.g. MRKGINM) or carboxyl terminus (e.g. GHHHHHH). These extensions presumably enable RNase G to cleave critically important cellular RNAs whose efficient processing or degradation ordinarily requires RNase E. That extending the amino terminus of RNase G restores growth to E. coli cells lacking RNase E without detectably improving tRNA processing suggests that RNase E is not essential for tRNA production and is required for cell growth because it plays an indispensable role in the maturation or decay of essential E. coli RNAs other than tRNA.
Deana
Atilio
A
Skirball Institute of Biomolecular Medicine and Department of Microbiology, New York University School of Medicine, NY 10016, USA.
Belasco
Joel G
JG
D004722:Endoribonucleases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D029968:Escherichia coli Proteins / Q000235:genetics / Q000502:physiology; D017353:Gene Deletion; D015870:Gene Expression; D020043:Genes, Essential; D005816:Genetic Complementation Test; D009154:Mutation; D012322:RNA Precursors / Q000378:metabolism; D012329:RNA, Bacterial / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D012335:RNA, Ribosomal / Q000378:metabolism; D012343:RNA, Transfer / Q000378:metabolism; D011995:Recombination, Genetic
D029968:Escherichia coli Proteins; D012322:RNA Precursors; D012329:RNA, Bacterial; D012333:RNA, Messenger; D012335:RNA, Ribosomal; D012343:RNA, Transfer; D004722:Endoribonucleases; C081905:rng protein, E coli; C022537:ribonuclease E