Table III. Mutagenesis of catalytically important residues in GRESAG4.1.

Mutation	Specific activity(% wild type)	Correlate inmammalian ACs	Context inmammalian ACs(Tesmer et al., 1997)	Vmax
D906A	0.005	Mg2+ coordination	D396 VC1	–
E943A	0.08	salt bridge to R934	K936 IIC2 (salt bridge to D923; C1–C2 interface)	wild type 10-fold decreased (Tang et al., 1995)
K945A	0.1	binds to N1 of adenine	K938 IIC2 (salt bridge to D1018 IIC2)	wild type (Tang et al., 1995)
D949A	0.008	Mg2+ coordination	D440 VC1	<10-fold inactive (Tang et al., 1995)
R1022A	60	γ-phosphate binding	R484 VC1	wild type10-fold decreased (Tang et al., 1995)
N1049A	0.03	active site structure,water coordination	N1025 IIC2	<10-fold-inactive (Yan et al., 1997)
R1053A	0.1	stabilization of transition state, binds to α- and/orβ-phosphate	R1029 IIC2	<10-fold- inactive (Tang et al., 1995; Yan et al., 1997)
E1055A	54	(salt bridge to R1022 inGRESAG4.1)	E518 VC1 (salt bridge to R484)	wild type (Tang et al., 1995; Dessauer et al., 1997)