Table 2.

Summary of MTSEA modification data.

MUTANT	MTSEA	modification rate	× 103, M-1 S-1 (n)
	control	+ ACh	+ Ba2+
M37C	2.4 ± .03 (10)	0.30 ± 0.05 (4)	0.40 ± 0.02 (5)
M40C	16 ± 0.2 (13)	2.2 ± 0.4 (3)	2.8 ± 0.05 (7)
N52C	0.40 ± .08 (9)	1.4 ± 0.04 (7)	0.26 ± 0.02 (7)
E44C	23 ± 0.7 (4)	0.90 ± 0.05 (4)	9.3 ± 0.1(8)
N170Ca	3.3 ± .05 (7)	5.7 ± 0.1 (7)	3.7 ± 0.06 (9)
E172Ca	15 ± 0.4 (5)	3.5 ± 0.1 (5)	7.3 ± 0.3 (6)
M40C/E172Qa	14 ± 0.5 (5)	1.3 ± 0.1 (5)	2.0 ± 0.3 (6)

Second-order rate constants ± standard error for various conditions at each Cys mutant. (n), number of determinations.

(a) Mutants studied using co-expression with human RIC-3 (Halevi et al., 2002).