Crystallographic structure of the turbine C-ring from spinach chloroplast F-ATP synthase.

In eukaryotic and prokaryotic cells, F-ATP synthases provide energy through the synthesis of ATP. The chloroplast F-ATP synthase (CFF-ATP synthase) of plants is integrated into the thylakoid membrane via its F-domain subunits a, b, b' and c Subunit c with a stoichiometry of 14 and subunit a form the gate for H-pumping, enabling the coupling of electrochemical energy with ATP synthesis in the F sector.Here we report the crystallization and structure determination of the c14-ring of subunit c of the CFF-ATP synthase from spinach chloroplasts. The crystals belonged to space group C2, with unit-cell parameters a=144.420, b=99.295, c=123.51 Å, and β=104.34° and diffracted to 4.5 Å resolution. Each c-ring contains 14 monomers in the asymmetric unit. The length of the c-ring is 60.32 Å, with an outer ring diameter 52.30 Å and an inner ring width of 40 Å.