Abstract
The crystal structure of PSII dimer from Thermosynechococcus vulcanus with its psbTc gene inactivated by insertion mutation of an antibiotic cassette in a site in the C-terminal region, was analyzed at 3.8 Å resolution. In the crystal structure of the mutant PSII, the transmembrane helix of PsbTc remains existed, whereas the stromal loop of PsbTc disappeared. In addition, the PsbM subunit, which is lost in a mutant PSII of T. elongatus lacking psbTc, was still present. While the content of PSII monomer was increased in the psbTc-disrupted mutant than that in the wild type, the dimeric form was still the major one in the mutant. These results indicated that the psbTc-disrupted mutant of T. vulcanus lacks only the stromal loop of PsbTc, which did not affect the binding of PsbM but partially destabilized the dimeric form of PSII, leading to the increase of PSII monomer.
