Figure 4

Barium alters the rate of MTSEA modification at inner β sheet residues. (A) Using the protocol described in Figure 3, we determined second-order rate constants for three reporter residues in the α7 AChR inner β sheet (M³⁷C, M⁴⁰C, and N⁵²C). Mean values for second-order rate constants for modification by MTSEA alone (control), MTSEA + ACh, and MTSEA + Ba²⁺ are shown. * Rate was significantly different from control (P < 0.05). (B) A plot of the ratios of second-order rate constants. Ba²⁺ and ACh both slowed the rates of modification of M³⁷C and M⁴⁰C. At N⁵²C, however, the rate of modification in the presence of Ba²⁺ was not significantly different from control, while ACh accelerated the modification rate. See Table 2 for summary including (n) for each condition.