The coxBAC Operon Encodes a Cytochrome c Oxidase Required for Heterotrophic Growth in the Cyanobacterium Anabaena variabilis Strain ATCC 29413

Abstract

Three genes, coxB, coxA, and coxC, found in a clone from a gene library of the cyanobacterium Anabaena variabilis strain ATCC 29413, were identified by hybridization with an oligonucleotide specific for aa 3 -type cytochrome c oxidases. Deletion of these genes from the genome of A. variabilis strain ATCC 29413 FD yielded strain CSW1, which displayed no chemoheterotrophic growth and an impaired cytochrome c oxidase activity. Photoautotrophic growth of CSW1, however, was unchanged, even with dinitrogen as the nitrogen source. A higher cytochrome c oxidase activity was detected in membrane preparations from dinitrogen-grown CSW1 than from nitrate-grown CSW1, but comparable activities of respiratory oxygen uptake were found in the wild type and in CSW1. Our data indicate that the identified cox gene cluster is essential for fructose-dependent growth in the dark, but not for growth on dinitrogen, and that other terminal respiratory oxidases are expressed in this cyanobacterium. Transcription analysis showed that coxBAC constitutes an operon which is expressed from two transcriptional start points. The use of one of them was stimulated by fructose.

Newly Identified Cytochrome c Oxidase Operon in the Nitrogen-Fixing Cyanobacterium Anabaena sp. Strain PCC 7120 Specifically Induced in Heterocysts

“…The major terminal oxidase of the electron transport chain in cyanobacteria is a mitochondrial-type cytochrome caa 3 oxidase (2). Thus, cytochrome c oxidase may play a critical role both in dissipating O 2 and in supplying the large ATP requirement of nitrogenase.An operon encoding subunits I, II, and III of the mitochondrial-type cytochrome caa 3 oxidase has been cloned from several cyanobacterial species (1,24,36,41). In this report, we describe two operons that each encode all three core subunits of a cytochrome c oxidase.…”

“…An operon encoding subunits I, II, and III of the mitochondrial-type cytochrome caa 3 oxidase has been cloned from several cyanobacterial species (1,24,36,41). In this report, we describe two operons that each encode all three core subunits of a cytochrome c oxidase.…”

“…A mutant disrupted in the coxAII gene, which encodes subunit I of the heterocyst-specific cytochrome c oxidase, exhibits no growth defects in either the presence or absence of fixed nitrogen. We have also cloned a second cytochrome c oxidase operon, coxBACI, that appears to be the ortholog of the previously described coxBACI operon of Anabaena variabilis (36). The coxBACI operon is expressed in all cells, and its expression is slightly increased in response to nitrogen limitation, although that expression returns to the prelimitation level before mature heterocysts have formed.…”

“…strain PCC 6803 ctaD (GenBank accession number X53746 [1,24]); Anabaena sp. strain ATCC29413 (A. variabilis) coxAI (GenBank accession number Z98264 [36]); Anabaena sp. strain PCC 7120 coxAI (this study and reference 23); and Paracoccus denitrificans COI (GenBank accession number X05829 [33]).…”

“…strain PCC 7120 coxBI sequence was obtained from a PCR product amplified from Anabaena sp. strain PCC 7120 DNA with primers varcoxB1-34 and varcoxA1503, which were derived from the sequence of A. variabilis coxBACI (36). Additional sequence upstream of coxBI was obtained by circularizing an NheI genomic digest and amplifying across the point of ligation with primers varcoxB223 and varcoxBinternal521.…”