TABLE 1.

Nucleotide exchange rates of the W-loop cysteine mutants of yeast actin

All rates are the mean values of at least three determinations. S.D. are given next to the rate values. Under identical conditions, the nucleotide release rates of rabbit skeletal actin were 0.0011 ± 0.0002 and 0.0053 ± 0.0005 s⁻¹ in the presence of Ca²⁺ and Mg²⁺ cations, respectively. TMR, tetramethylrhodamine-5-maleimide.

Divalent cation	K-ϵ-ATP
	WT	A167C	S170C	F169C	F169C-TMR	F169C- Fluor
				s−1
0.2 mm Ca2+	0.013 ± 0.002	0.012 ± 0.006	0.0017 ± 0.0004	0.006 ± 0.001	0.006 ± 0.002-	0.005 ± 0.002
0.1 mm Mg2+	0.121 ± 0.003			0.07 ± 0.01	0.013 ± 0.004	0.014 ± 0.006