Fig. 5.

Nucleotide inhibition of RNase R^Ps activity on malE-malF and poly(A) substrates. ³²P-labeled substrates were used for degradation at 25°C. (A) Degradation activity of RNase R^Ps on intergenic malE-malF RNA substrate, which contains a REP sequence with stem-loop structures (17, 21). (B) Effects of ATP, ADP, and AMP on RNase R-mediated degradation of 5′-end-labeled poly(A). (C and D) The effects of the nucleotides UTP, CTP, GTP, and dATP and inhibition by nonhydrolyzable ATP-γS of RNase R^Ps on poly(A) and malE-malF RNA degradation are shown in panels C and D, respectively. A total of 10 ng of RNase R and 5 mM nucleotides were used in the reaction mixtures in panel C. Lanes C represent control samples (without the enzyme), while lanes E represent the second control with enzyme but without any added nucleotides.