Kinetics of conformational transitions of demetalized Concanavalin A

Demetalized Concanavalin A exists in two conformational states, known as locked (PL) and unlocked (P) [Brown et al., Biochemistry 16, 3883 (1977)]. The equilibrium ratio [PL] [P] is 0.14±0.01 at 25 °C, pH 6.4 [Brown et al., Biochemistry 21, 465 (1982)]. We now report values of the rate constants for the P ái PL equilibrium; k₁ = (33±4 h)^-1 and k_-1 = (4.6±0.6 h)^-1 for the P → PL and PL → P transitions, respectively, at 25 °C, pH 6.4. The experiments utilize the fact that saccharide binds to PL [Koenig et al., Biochemistry 17, 4251 (1978)], producing a time-dependent increase in the total concentration of locked forms at equilibrium, and use a new technique for measuring this concentration.