Table 1.

Effect of Mja RPPs on the rate of cleavage of pre-tRNA^Tyr-Mja (WT) and -Mja ΔU (MT) at 55°C

Assayed under optimal conditions for each catalytic entity	[NH4+]; [Mg2+], M	kobs (WT), min−1*	Rel. kobs (WT)	kobs (MT), min−1**	Rel. kobs (MT)	kobs(WT)/kobs(MT)
pre-tRNATyr-Mja RPR (WT or ΔU MT)	2.5; 0.5	0.2 ± 0.04	1	0.0025 ± 0.0002	1	80
+ RPP21•RPP29	0.8; 0.1	0.24 ± 0.04	1	0.017 ± 0.0014	7	14
+ POP5•RPP30	0.8; 0.1	20 ± 0.32	100	1.46 ± 0.12	584	14
+ Both binary RPP complexes	0.8; 0.1	22 ± 0.16	105	1.84 ± 0.18*	736	12

^*These rates at pH 6 were extrapolated from those determined at pH 5.4 and reported by us previously.¹⁶ We had also earlier established the direct relationship between log (k_obs) versus pH.¹⁶

^**Experiments were performed at pH 6, except for pre-tRNA^Tyr-Mja ΔU RPR reconstituted with both binary RPP complexes, which was assayed at pH 5.4. The rate at pH 6 for the reaction with four RPPs was obtained by extrapolation from 5.4. The standard errors of the curve fits shown in Figure 3 are indicated in the estimates of k_obs.