Nucleic Acids Research Advance Access first published online on March 13, 2007
This version published online on April 2, 2007
Nucleic Acids Research, doi:10.1093/nar/gkm005
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In vivo and in vitro investigation of bacterial type B RNase P interaction with tRNA 3'-CCA
Institut für Pharmazeutische Chemie, Philipps-Universität Marburg, Marbacher Weg 6, D-35037 Marburg, Germany
*To whom correspondence should be addressed. Tel: +6421 2825827; Fax: +6421 2825854; Email: roland.hartmann{at}staff.uni-marburg.de
Received November 6, 2006. Revised December 22, 2006. Accepted December 22, 2006.
For catalysis by bacterial type B RNase P, the importance of a specific interaction with p(recursor)tRNA 3'-CCA termini is yet unclear. We show that mutation of one of the two G residues assumed to interact with 3'-CCA in type B RNase P RNAs inhibits cell growth, but cell viability is at least partially restored at increased RNase P levels due to RNase P protein overexpression. The in vivo defects of the mutant enzymes correlated with an enzyme defect at low Mg2+ in vitro. For Bacillus subtilis RNase P, an isosteric C259-G74 bp fully and a C258-G75 bp slightly rescued catalytic proficiency, demonstrating Watson–Crick base pairing to tRNA 3'-CCA but also emphasizing the importance of the base identity of the 5'-proximal G residue (G258). We infer the defect of the mutant enzymes to primarily lie in the recruitment of catalytically relevant Mg2+, with a possible contribution from altered RNA folding. Although with reduced efficiency, B. subtilis RNase P is able to cleave CCA-less ptRNAs in vitro and in vivo. We conclude that the observed in vivo defects upon disruption of the CCA interaction are either due to a global deceleration in ptRNA maturation or severe inhibition of 5'-maturation for a ptRNA subset.