Effects of terminal deletions in C5 protein on promoting RNase P catalysis

Deletion derivatives of C5 protein, the protein cofactor of Escherichia col i RNase P, were constructed as soluble MBP (maltose-binding protein) fusion proteins to assess the deletion effects on promoting RNase P catalysis and on binding to M1 RNA, the catalytic subunit of the enzyme. The C5 protein, with large terminal deletions, retained its promoting activity of RNase P catalysis under protein excess conditions in vitro, Some deletion derivativ es complemented the temperature sensitive phenotype of E. coli A49 cells ca rrying the rnpA49 mutation. This ability also suggests that part of the C5 protein is enough to produce the catalytic activity of RNase P in vivo. Bot h the central conserved region, called the RNR motif, and the C-terminal re gion are essential for the binding of C5 protein to M1 RNA. Meanwhile, the N-terminal region contributes to promoting RNase P catalysis in ways other than binding to M1 RNA. (C) 2000 Academic Press.