Structure of Ptrotozoan Cytochromes
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Date
1974Author
Pettigrew, Graham Walter
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Abstract
C-type cytochromes from two protozoa, Crithidia oncopelti and
Kuglena gracilis. were purified and partly characterised.
Crithidia cytochrome C557 and Euglena cytochrome C558 had certain
atypical spectral characteristics. The sequence of amino acids in both
proteins was determined and compared with the large number of eukaryotic
cytochrome c sequences already known. One of the two amino acids which
are involved in the covalent attachment of the prosthetic group to the
protein in c-type cytochromes is replaced by a non-binding amino acid in
both protozoan cytochromes. It is proposed that this change results in
the observed spectral peculiarities of these two cytochromes.
A second c—type cytochrome, which is implicated in photosynthesis,
was isolated from Euglena and the sequence of amino acids was determined.
This protein is not closely related in structure to the mitochondrial
cytochromes c although certain features are similar. Homology with a
prokaryotic c—type cytochrome is proposed, with possible implications for
the evolution of photosynthesis.