Table 3.

Distance of His64 imidazole group from Zn${}^{2+}$ for the “in” and “out” conformations. All distances are measured from the His64 imidazole ring centroid to the Zn${}^{2+}$. Faux refers to other conformations observed excluding traditional “in” and “out” occupied by His64.

Variant	Imidazole-Zn${}^{2+}$ Distance (Å)
	apo			BCT			CO${}_2$
	In	Out	Faux in	In	Out	Faux in	In	Out	Faux in
K18E	8.65	*	7.30	8.08	11.09	*	6.96	11.20	*
K18Q	8.11	11.01	*	8.22	*	*	8.96	10.42	*
H107Y	8.50	10.63	*	8.24	10.86	*	7.98	10.67	*
P236H	8.57	11.26	*	8.70	12.02	*	7.12	11.71	*
P236R	8.26	11.02	7.36	7.99	10.84	*	7.50	10.43	*
N252D	8.11	11.33	*	8.65	10.93	*	8.63	11.20	*
WT	8.24	11.21	*	8.57	11.07	*	8.45	11.31	*

* Conformation not observed.