A novel function of RNase P from Escherichia coli: processing of a suppressor tRNA precursor.
The leuX gene of Escherichia coli codes for a suppressor tRNA and forms a single gene operon containing its own promoter and Q-independent terminator. An analysis of the in vitro processing of leuX precursor revealed that the processing of the 5' end took place in a single-step reaction catalysed by RNase P while the 3' processing involved two successive reactions. The endonucleolytic cleavage activity of the 3' precursor sequence was found to copurify with RNase P. Heat inactivation of thermosensitive RNase P from two independent E. coli mutants abolished the cleavage activity of both the 5' and 3' ends. These results altogether suggest that RNase P carries the activity of 3' end cleavage as well as that of 5' processing. In the presence of Mg2+ alone, the leuX precursor was found to be self-cleaved at a site approximately 13 nt inside from the 5' end of mature tRNA. The self-cleaved precursor tRNA was no longer processed by the 3' endonuclease, suggesting that the 3' endonuclease recognizes a specific conformation of the precursor tRNA for action.
Nomura
T
T
Department of Molecular Genetics, National Institute of Genetics, Shizuoka, Japan.
Ishihama
A
A
D001483:Base Sequence; D004722:Endoribonucleases / Q000378:metabolism*; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics; D029968:Escherichia coli Proteins; D006358:Hot Temperature; D008969:Molecular Sequence Data; D012322:RNA Precursors / Q000235:genetics / Q000378:metabolism*; D012323:RNA Processing, Post-Transcriptional; D012343:RNA, Transfer / Q000235:genetics / Q000378:metabolism*; D043262:Ribonuclease P; D014158:Transcription, Genetic
D029968:Escherichia coli Proteins; D012322:RNA Precursors; D012343:RNA, Transfer; D004722:Endoribonucleases; D043262:Ribonuclease P; C470865:ribonuclease P, E coli