Site-directed mutagenesis of ε subunit of ATP synthase of maize chloroplast

The effects of some residues in maize chloroplast epsilon subunit on its activity have been studied by site-directed mutagenesis. After replacing Thr-42 of epsilon subunit with Cys, Arg, Ile or Pro, and forming the mutant epsilon T42C, mutant epsilon T42R, mutant epsilon T42I and mutant epsilon T42P respectively, it was found that the mutant epsilon T42P protein could no longer be expressed, but expression of other epsilon subunit mutants was similar to that of wild type. Comparing the inhibitory potency of different mutants of epsilon subunit with that of the wild type, it was found that the inhibitory effects of epsilon subunit mutants epsilon T42C and epsilon T42R on ATPase activity were slightly higher than that of wild type, but the epsilon T42I protein strongly inhibited the Ca2+-ATPase activity.