Endonucleolytic processing of 5′ 32P-labeled ptRNAGly by RNase P holoenzymes at 37°C. (A) RNase P activity test in the presence of protein A Sepharose beads coated with antibodies from three different sera (preimmune serum and antisera specific for T. thermophilus transcription factor NusG or C587) and preincubated with a T. thermophilus DEAE chromatography fraction enriched in RNase P activity. (B) Activation of T. thermophilus RNase P RNA (400 nM) by C551 (80 nM); assay conditions were 37°C, 50 mM Mes, 0.1 M NH4OAc, 10 mM Mg(OAc)2, pH 6.0, < 1 nM ptRNAGly.