Aspects of RNase P Structure and Function

Abstract

Both genetic and biochemical studies have shown that RNase P is an endoribonuclease that is necessary for the processing of all precursor tRNAs in Escherichia coli (for reviews, see Smith 1976; McClain 1977; Altman 1978a,b). Some important features of the pathways of RNA processing are illustrated by the manner in which the substrates for this enzyme were first isolated, and by the way the enzyme itself was first identified. In this paper we shall detail some of the chronology of studies of RNase P and the nature of the interaction of the enzyme with its substrates. In addition we will summarize some biochemical studies of RNase-P-like activities in tRNA biosynthesis in eukaryotes.

PATHWAY ANALYSIS
The analysis of the metabolism or catabolism of small molecules in microorganisms has traditionally relied on the availability of mutant enzymes in the pathway. The absence of wild-type enzyme made possible the accumulation of its immediate substrate in the pathway. In the analysis of tRNA biosynthesis, in addition to mutant enzymes, one can also isolate mutants in the initial substrates of the pathway, tRNA precursor molecules, since these are macromolecules with nucleotide sequences encoded in DNA. Certain mutations in tRNA genes yield transcripts that interact less efficiently than the wild-type transcripts with the tRNA processing enzymes (Altman et al. 1974). As a result, these gene transcripts temporarily accumulate in vivo. These mutants can be isolated most easily in cells carrying suppressor tRNA genes by looking for loss of suppression. The loss of the suppressing phenotype is...