Euglena cytochrome

Fig. 2. Dependence of values on ionic strength, /. for Euglena cytochrome c-552 measured at pH 3.0, 4.8, and 7.0, where the net charge, z, on the protein is positive, nearly zero, and negative, respectively. [Adapted from Ref. (14).]...

Cytochrome c552 from Euglena gracilis (also known as cytochrome / or c6) contains 87 amino acid residues, two hemes and one flavin per molecule.693 NMR studies706 indicate that the chirality of the axial methionine is similar to that of cytochrome c but different from cytochrome c5Sl. Rapid intramolecular transport has been demonstrated by the use of pulsed laser excitation, and the measurement of reduction kinetics. Both flavin and heme groups are reduced simultaneously on a multisecond time scale, with the transient formation of a protein-bound flavin anion radical.707... 

R. palustris has an even more extended 80 s loop. Micrococcus denitrificans C550 and R. capsulata a are remarkably similar molecules, differing by no more than the cytochromes c of spinach and Euglena. In spite of the difference in metabolic roles, respiration vs. photosynthesis, csso seems like a perfectly normal member of the cj class. 

Cytochrome be has been purified to the electrophoretically homogeneous state by Stuart and Wasserman 24 )- This cytochrome is reduced by dithionite but not by ascorbate. The reduced form is autoxidizable and does not combine with CO. Its molecular weight was determined to be 40,000 on the basis of heme content. A similar cytochrome, showing the a band at 561-563 nm, has been observed in several species of green algae 203,242-251), Euglena 252,253), and red algae 254). 

A few respiratory type b cytochromes, which have an a band of around 562 nm but are distinct from photosynthetic cytochrome bt, have been reported to exist in Euglena and green algae (247,249, 6). 

One should also emphasize that during the greening of Euglena, as well as of the etiolated higher plants in which proplastids are present, not only photosynthetic membranes are formed, but also most of the soluble enzymes of the chloroplast—such as Ru-1, 5-diP carboxylase, G-3-P dehydrogenase, cytochrome 552, etc., as well as chloroplast ribosomes. 

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