- PMID:
9153077
- Authors:
- Okorokov AL, Panov KI, Offen WA, Mukhortov VG, Antson AA, Karpeisky MYa, Wilkinson AJ, Dodson GG
- Title:
- RNA cleavage without hydrolysis. Splitting the catalytic activities of binase with Asn101 and Thr101 mutations.
- Journal:
- Protein Eng. 1997 Mar;10(3):273-8.
- Abstract:
- Members of the microbial guanyl-specific ribonuclease family catalyse the endonucleolytic cleavage of single-stranded RNA in a two-step reaction involving transesterification to form a 2',3'-cyclic phosphate and its subsequent hydrolysis to yield the respective 3'-phosphate. The extracellular ribonuclease from Bacillus intermedius (binase, RNase Bi) shares a common mechanism for RNA hydrolysis with mammalian RNases. Two catalytic residues in the active site of binase, Glu72 and His101, are thought to be involved in general acid-general base catalysis of RNA cleavage. Using site-directed mutagenesis, binase mutants were produced containing amino acid substitutions H101N and H101T and their catalytic properties towards RNA, poly(I), poly(A), GpC and guanosine 2',3'-cyclic phosphate (cGMP) substrates were studied. The engineered mutant proteins are active in the transesterification step which produces the 2',3'-cyclic phosphate species but they have lost the ability to catalyse hydrolysis of the cyclic phosphate to give the 3' monophosphate product.