TABLE 1.

Mutational effects on GTP methylation, guanylation of the protein, and AdoMet-binding ability

Wild type or mutant	GTP methylation (%)a	Guanylation (%) in the presence of:		Binding of AdoMetd
		m7GTP and AdoHcyb	GTP and AdoMetc
Wild type	100	100	100	++++
H66A	<1	∼0	∼0	−
H68A	980	∼0	∼0	+++++
K121A	20	2	7	−
D122A	3	∼0	∼0	−
R125A	3	∼0	∼0	−
Y213A	2	∼0	∼0	−
K218A	120	73	49	++
C234A	28	21	15	+
D310A	10	12	5	±
W312A	37	35	18	+±
R316A	51	34	19	+++
K344A	14	12	14	+
W377A	120	NDe	100	+++±
K389A	150	ND	110	+++±
W406A	14	8	1	±
K409A	59	ND	40	++

^aGTP methyltransferase activity (reaction 1) was measured based on the amount of methyl group transferred from S-ado[methyl-³H]Met to GTP. The data are from Fig. 5.

^bGuanylation of the enzyme when [α-³²P]m⁷GTP and AdoHcy were used as substrates (reaction 2). The data are derived from the respective pixels shown in Fig. 11. Activities under the detectable level are presented as ∼0%.

^cGuanylation of the enzyme when [α-³²P]GTP and AdoMet were used as substrates (reaction 3, which is presumably equivalent to reaction 1 plus reaction 2). The data are from Fig. 4B. Activities under the detectable level are presented as ∼0%.

^dAdoMet-binding abilities of the enzymes were estimated from the UV cross-linking data shown in Fig. 4C. The symbol “+” and “±” indicate approximate 25 and 10% binding abilities, respectively, of that of the wild-type enzyme, whereas “−” indicates an indiscernible binding ability.

^eND, not determined.