. Author manuscript; available in PMC: 2021 Aug 15.

Published in final edited form as: Biochemistry. 2020 Jun 15;59(25):2359–2370. doi: 10.1021/acs.biochem.0c00212

Table 1.

Characteristics of ³¹P field cycling NMR parameters associated with WT GMPR in the hydride transfer (E•IMP•NADP⁺, HT) and deamination (E•GMP•NADP⁺, DA) complexes.

³¹P	Comparison	P ^a	Implication
Substrate mono-P	τ_D (HT) ~ τ_D (DA)	0.13	Bound substrate ³¹P mobility is the same for both IMP and GMP; τ_D smaller than that of overall GMPR rotation, suggesting that the substrate is mobile in the active site
	R_D0 (HT) < R_D0 (DA)	0.015	GMP interacts with fewer ¹H in DA than IMP in HT
	τ_D/R_D0 (HT) < τ_D/R_D0 (DA)	0.005	Effective r_PH is longer for bound GMP (¹H fewer or farther away)
NADP⁺ mono-P	τ_D (HT) > τ_D (DA) ^b	0.004	Bound NADP⁺ is more mobile in DA
	R_D0 (HT) > R_D0 (DA)	0.009	¹H dipolar relaxation is significantly higher in HT
	τ_D/R_D0 (HT) < τ_D/R_D0 (DA)	0.014	r_PH is shorter for the bound cofactor mono-P in HT
NADP⁺ di-P ^b	τ_D (HT) > τ_D (DA) ^b	0.049	Bound NADP⁺ is more mobile in DA
	R_D0 (HT) > R_D0 (DA)	0.029	¹H dipolar relaxation is significantly higher in HT
	τ_D/R_D0 (HT) < τ_D/R_D0 (DA)	0.041	Effective r_PH is smaller for HT
IMP vs NADP⁺ ^b	τ_D (IMP) < τ_D (NADP⁺)	0.003	The cofactor is more rigid than substrate in HT; cofactor τ_D approximates that of overall GMPR rotation
GMP vs NADP⁺ di-P ^b	τ_D (GMP) > τ_D (NADP⁺)	0.024	The cofactor has more mobility than substrate in DA

The comparisons were done with an unpaired student t-test and significance indicated by P<0.05.

Statistics are given for only one of the diphosphate nuclei because the values are indistinguishable.