Table 3.

pH dependence of metal/Pce stoichiometry in the wildtype enzyme and the H90A mutant

Protein	Mediuma	Zn2+b	Ca2+
Wild type	Bis-Tris (pH 5.5)	2.2	2.4
Wild type	HEPES (pH 7.0)	2.0	2.1
Wild type	Bis-Tris-propane (pH 8.0)	2.3	N.D.c
Wild type	Bis-Tris-propane (pH 9.0)	2.0	2.5
H90A	Bis-Tris (pH 5.5)	1.2	3.1
H90A	HEPES (pH 7.0)	2.4	1.9
H90A	Bis-Tris-propane (pH 9.0)	2.1	1.9

^a Unless otherwise stated the [Zn²⁺]_free in all buffers was 3 μM.

^b Estimated errors in metal content are below 5%.

^c N.D., not determined.