Characterisation of an opcA Mutant of the Unicellular Cyanobacterium Synechocystis sp. PCC 6803

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Web End = Curr Microbiol (2015) 71:572578

DOI 10.1007/s00284-015-0889-4

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Web End = Characterisation of an opcA Mutant of the Unicellular Cyanobacterium Synechocystis sp. PCC 6803

Kbrazkul1 Haydar Karakaya1

Received: 9 April 2015 / Accepted: 28 June 2015 / Published online: 9 August 2015 Springer Science+Business Media New York 2015

Abstract The genes opcA and zwf are located close to each other in most of cyanobacterial strains and the mutations in the opcA gene were reported to lose most of G6PDH activity. One of the reasons suggested for this loss was the polar effectof the mutationonexpressionof the zwf gene in the same operon and the other was absence of the OpcA polypeptide necessary for the catalytic activity of G6PDH. Synechocystis sp. PCC 6803 exhibits a gene organisation in which opcA and zwf are far away from each other and is ideal for analysis of an opcA mutation alone. In this study, an opcA single mutant and an opcA-zwf double mutant were constructed and effects of the opcA mutation on G6PDH activity and dark viability were then investigated. Contrary to the previous observations, no negative effect of the mutation on G6PDH activity was found under the optimal substrate concentrations. However, when one of the substrates, G6P or NADP, was reduced gradually, G6PDH activity in the mutant cells decreased faster than the wild types. Our results indicated that an opcA mutation did not affect G6PDH activity severely when zwf and opcA were in different operons. Similarly, dark viability of the opcA single and the zwf-opcA double mutants did not exhibit meaningful difference from the wild type.

Introduction

Since sequenced and determined rst in Nostoc punctiforme ATCC 29133 [16], Synechococcus sp. PCC 7942, and Anabaena sp. PCC 7120 [10], the opcA gene has been

reportedly attributed to be involved in the carbon metabolism enzymes especially in glucose-6-phosphate dehydrogenase (G6PDH). Compared to the wild type, an opcA mutant strain lost 98 % of G6PDH activity in N. punctiforme ATCC 29133. After wild-type copy of opcA was transferred to the mutant strain, G6PDH activity was completely...