PMID:2406134
| Citation |
Meador, J 3rd, Cannon, B, Cannistraro, VJ and Kennell, D (1990) Purification and characterization of Escherichia coli RNase I. Comparisons with RNase M. Eur. J. Biochem. 187:549-53 |
|---|---|
| Abstract |
The endoribonuclease, RNase I, was purified from the periplasm of Escherichia coli. Based on PAGE, it has molecular mass of approximately 27 kDa with a migration rate indistinguishable from that of the recently reported RNase M from E. coli. The amino acid sequence of the two enzymes must be very similar based on two-dimensional mapping of their tryptic peptides and suggests either a post-transcriptional modification to yield different proteins from the same gene or evolution of two genes by gene duplication. However, while RNase I could degrade each of the four ribonucleotide homopolymers, only poly(U) or poly(C) were good substrates for RNase M with possibly some hydrolysis of poly(A). The reaction rate for poly(C) hydrolysis with RNase M was about ten times faster than for poly(U), while for RNase I the rates were about equal. Besides differences in specificity, RNase M was only located in the spheroplasts while RNase I found in the periplasm of growing cells. In terms of function, RNase I is known to cause degradation of rRNA during periods of stress or non-growth, whereas it has been proposed that RNase M is the endonuclease for mRNA degradation in growing cells. |
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| Keywords |
Amino Acid Sequence; Electrophoresis, Polyacrylamide Gel; Endoribonucleases/genetics; Endoribonucleases/isolation & purification; Escherichia coli/enzymology; Escherichia coli/genetics; Kinetics; Peptide Mapping; Poly A/metabolism; Poly C/metabolism; Poly G/metabolism; Poly U/metabolism; RNA, Messenger/metabolism; RNA, Ribosomal/metabolism; Ribonuclease, Pancreatic/genetics; Ribonuclease, Pancreatic/isolation & purification; Substrate Specificity; Trypsin |
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