Cloning, sequencing and transcriptional studies of the genes for cytochrome c-553 and plastocyanin from Anabaena sp. PCC 7120.
In some cyanobacteria and eukaryotic algae, cytochrome c-553 (c-552) and plastocyanin function as alternative electron carriers between the cytochrome b6-f complex and Photosystem I. In these organisms plastocyanin is the electron carrier under copper-replete conditions, and cytochrome c-553 is the electron carrier during copper deprivation. In this paper we report the cloning, sequencing and transcriptional analysis of the genes for cytochrome c-553 and plastocyanin from Anabaena sp. PCC 7120. The gene for cytochrome c-553 encodes a preprotein containing 111 amino acids with a predicted N-terminal transit peptide sequence of 25 amino acids. The gene for plastocyanin encodes a preprotein containing 139 amino acids with a N-terminal transit peptide sequence of 34 amino acids. RNA transcript analyses indicate that the expression of the genes for cytochrome c-553 (petJ) and plastocyanin (petE) are regulated in reciprocal ways in response to copper concentration. In copper-replete conditions, petJ is expressed at very low levels, but is transcribed at high levels under copper deprivation; petE is down-regulated in the absence of copper, but is rapidly up-regulated when copper is added back to the medium.
Department of Botany, University of Toronto, Ontario, Canada.
M
M
Ghassemian
B
B
Wong
F
F
Ferreira
J L
JL
Markley
N A
NA
Straus
D000595:Amino Acid Sequence; D017033:Anabaena / Q000235:genetics*; D001483:Base Sequence; D003001:Cloning, Molecular; D003574:Cytochrome c Group / Q000235:genetics*; D015342:DNA Probes; D005798:Genes, Bacterial / Q000235:genetics*; D008969:Molecular Sequence Data; D010970:Plastocyanin / Q000235:genetics*; D021382:Protein Sorting Signals / Q000235:genetics; D012333:RNA, Messenger / Q000032:analysis; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D014158:Transcription, Genetic
D003574:Cytochrome c Group; D015342:DNA Probes; D021382:Protein Sorting Signals; D012333:RNA, Messenger; C083951:cytochrome c553; D010970:Plastocyanin; C022302:cytochrome C-552