Estimation of the rate constant k2. Half-life of the slow component as a function of the reciprocal value of the concentration of pc (A) and cyt c6 (B) concentration. PSI particles were isolated from wild-type (•), K12P transformant (□), K16Q transformant (Δ), K23Q transformant (◊), and the K30Q transformant (○). Measurements were performed in the presence of 10 mM MgCl2, except for wild-type PSI with pc (3 mM MgCl2).