Insertion of a Chloroplast psbA Gene Into the Chromosome of the Cyanobacterium Synechocystis 6803

Abstract

Photosystem (PS) II in the procaryotic cyanobacteria is structurally similar to that in higher plants and contains around 20 different polypeptide subunits [1]. The reaction center of PSII, harboring the key components for the charge separation, consists of the D1 and D2 polypeptides [2,3]. Our studies concern the biogenesis of PSII in the cyanobacterium Synechocystis 6803. We are particularly interested in the role of the D1 polypeptide in the assembly process. We have previously described [4] the construction of a S. 6803 mutant where synthesis of the D1 polypeptide has been inactivated by insertional mutagenesis of the psbA gene family, encoding the D1 polypeptide. A preliminary functional characterization of that mutant showed that the PSII activity was severely perturbed while PSI activity was unaffected [4,5]. The structural analysis revealed that despite the lack of the D1 and D2 polypeptides, mutant thylakoids still retained several intrinsic PSII polypeptides [1].