Isolation and Spectroscopic Characterization of Cytochrome C6 from cladophora Glomerata

Abstract

Cytochrome c6 (cyt c6) is a water soluble low-spin hemoprotein involved in electron transfer chain of oxigenic photosynthesis. It functions in photosynthetic membranes of some algae and cyanobacteria shuttling electrons between the two membrane-bond complexes, cytochrome b6/f and photosystem I [1]. In higher plants and advanced algal species cyt c6 is replaced by the blue-copper protein, plastocyanin [2]. The structures of the green algae Chlamydomonas reinhardtii and Monoraphidium braunii cyt c6 have been determined by X-ray crystallography [3, 4] and nuclear magnetic resonance (NMR) [5] techniques. Although a number of structural data are now available also for plastocyanin (for review see [2]), the peculiarities of these two evolutionarily unrelated proteins that allow them to perform the same function are not fully clarified. Detailed characterization of cyt c6 as well as plastocyanins obtained from various sources could help in understanding the evolution of these proteins. This paper reports the purification and spectroscopic properties of cyt c6 from the green algae Cladophora glomerata.