Table 2.

Enzymatic activity of wild-type M1 RNA and tetraloop mutants at varying concentrations of Mg²⁺

	[Mg2+], mM
	20	37.5	100	190
WT	1.0	1.0	1.0	1.0
L3m	0.93	ND	1.1	ND
L9m	0.66	ND	1.1	ND
L12m	0.68	ND	1.2	ND
L14m	<0.001	0.15	0.33	0.8
L18m	<0.001	0.002	0.07	0.48

Wild-type (WT) M1 RNA and L3m, L9m, and L12m were assayed at a concentration of 10 nM; L14m and L18m were assayed at concentrations of 20 nM and 40 nM, respectively. The pTyr concentration was 100 nM. Values are expressed as a fraction of substrate cleaved per min for mutant enzyme divided by substrate cleaved per minute for the WT M1 RNA. ND, not determined.