The Bacillus subtilis ribonucleasc P consists of a protein and an RNA. At high ionic strength the reaction is protein-independent; die RNA alone is capable of cleaving precursor transfer RNA, but the turnover is slow. Kinetic analyses show that high salt concentrations facilitate substrate binding in the absence of the protein, probably by decreasing the repulsion between die polyanionic enzyme and substrate RNAs, and also slow product release and enzyme turnover. It is proposed that die ribonuclease P protein, which is small and basic, provides a local pool of counter-ions diat facilitates substrate binding without interfering with rapid product release.
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