Cytochrome f from the Antarctic psychrophile, Chlamydomonas raudensis UWO 241: structure, sequence, and complementation in the mesophile, Chlamydomonas reinhardtii

• Published in: Molecular genetics and genomics : MGG 2006-04, Vol.275 (4), p.387-398
• Main Authors: Gudynaite-Savitch, Loreta, Gretes, Michael, Morgan-Kiss, Rachael M, Savitch, Leonid V, Simmonds, John, Kohalmi, Susanne E, Hüner, Norman P. A
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Amino acids; Animals; Antarctic Regions; Arabidopsis Proteins - genetics; Bacteria; Chlamydomonas; Chlamydomonas - genetics; Chlamydomonas raudensis; Chlamydomonas reinhardtii; Chlamydomonas reinhardtii - genetics; Chloroplasts - genetics; Cloning, Molecular; cytochrome f; Cytochromes f - chemistry; Cytochromes f - genetics; Cytochromes f - metabolism; E coli; electron transfer; Electron Transport; Enzyme Stability; Enzymes; Escherichia coli; Escherichia coli - genetics; Genetic Complementation Test; Molecular Sequence Data; Molecular Weight; Mutation; Protein Conformation; Sequence Analysis; State transitions; thermal stability
• ISSN: 1617-4615; 1617-4623
• DOI: 10.1007/s00438-005-0094-4

Although cytochrome f from the Antarctic psychrophile, Chlamydomonas raudensis UWO 241, exhibits a lower apparent molecular mass (34 kD) than that of the mesophile C. reinhardtii (41 kD) based on SDS-PAGE, both proteins are comparable in calculated molecular mass and show 79% identity in amino acid sequence. The difference in apparent molecular mass was maintained after expression of petA from both Chlamydomonas species in either E. coli or a C. reinhardtii ΔpetA mutant and after substitution of a unique third cysteine-292 to phenylalanine in the psychrophilic cytochrome f. Moreover, the heme of the psychrophilic form of cytochrome f was less stable upon heating than that of the mesophile. In contrast to C. raudensis, a C. reinhardtii ΔpetA mutant transformed with petA from C. raudensis exhibited the ability to undergo state transitions and a capacity for intersystem electron transport comparable to that of C. reinhardtii wild type. However, the C. reinhardtii petA transformants accumulated lower levels of cytochrome b ₆ /f complexes and exhibited lower light saturated rates of O₂ evolution than C. reinhardtii wild type. We show that the presence of an altered form of cytochrome f in C. raudensis does not account for its inability to undergo state transitions or its impaired capacity for intersystem electron transport as previously suggested. A combined survey of the apparent molecular mass, thermal stability and amino acid sequences of cytochrome f from a broad range of mesophilic species shows unequivocally that the observed differences in cytochrome f structure are not related to psychrophilly. Thus, caution must be exercised in relating differences in amino acid sequence and thermal stability to adaptation to cold environments.