Deletion of cytochrome c oxidase genes from the cyanobacterium Synechocystis sp. PCC6803: Evidence for alternative respiratory pathways

Abstract

An oligonucleotide directed against a highly conserved region of aa3-type cytochrome c oxidases was used to clone the cox genes from the cyanobacterium Synechocystis sp. PCC6803. Several overlapping clones were obtained that contained the coxB, coxA, and coxC genes, transcribed in the same direction in that order, coding for subunits II, I, and III, respectively. The deduced protein sequences of the three subunits showed high sequence similarity with the corresponding subunits of all known aa3-type cytochrome c oxidases. A 1.94-kb HindII fragment containing most of coxA and about half of coxC was deleted and replaced by a cassette coding for kanamycin resistance. Mutant cells that were homozygous for the deleted cox locus were obtained. They were viable under photoautotrophic and photoheterotrophic conditions, but contained no cytochrome c oxidase activity. Nevertheless, these mutant cells showed almost normal respiration, defined as cyanide-inhibitable O2 uptake by whole cells in the dark. It is concluded, therefore, that aa3-type cytochrome c oxidase is not the only terminal respiratory oxidase in Synechocystis sp. PCC6803.

Coordinated transporter activity shapes high-affinity iron acquisition in cyanobacteria

“…In addition, experiments with wild-type cells incubated with the photosynthetic inhibitor, 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU), did not affect Fe uptake rates but caused an increase in iron reduction rates (Supplementary Figure S2). As both photosynthetic and respiratory chains in cyanobacteria share a quinone/quinol pool (Schmetterer et al, 1994), the inhibition of photosynthesis may increase respiratory electron flow through Cytb 6 f. Does respiratory electron flow have a role in reductive iron uptake?…”

“…Two of these-a cytochrome c oxidase (Cox) and a quinol oxidase (Cyd)-are important in cellular respiration (Alge and Peschek, 1993;Schmetterer et al, 1994;Howitt and Vermaas, 1998). The function of the third, the Alternate Respiratory Terminal Oxidase (ARTO), or CtaII, remained unclear.…”

Cytochromeb/fComplex Is Not Involved in Respiration in the CyanobacteriumSynechocystisPCC 6803 Grown Photoautotrophycally

“…The existence ofa cytochrome c oxidase in cyanobacteria has been shown,5 7) and therefore the respiratory electron transport has been considered to pass through a cytochrome hlf complex and cytochrome ('553 (or plastocyanin). However, Schmetterer et al 8 ) have demonstrated that mutant strains of Synechocystis pec 6803. in which aa3-type oxidase was genetically destroyed, had significant respiratory oxygen uptake.…”

Sll1717 Affects the Redox State of the Plastoquinone Pool by Modulating Quinol Oxidase Activity in Thylakoids

“…Factors influencing the redox state of the PQ pool may therefore influence intracellular processes. To aid in studying these processes, a series of mutants with lesions in photosynthetic and respiratory proteins have been developed (7,11,17,28,29,32,33).…”

“…One of these mutants lacks CtaI (32). This mutant is unable to grow at low light intensity, even in the presence of glucose, presumably because of overreduction of the PQ pool in thylakoids.…”