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Title: Study of the cytochrome C3 from Shewanella NCIMB400 and the flavocytochrome B2 from Saccharomyces cerevisiae
Author: Pike, Andrew
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1998
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A cytochrome c3 has been purified from Shewanella sp. NCIMB400 and the gene encoding it, cycA has been cloned and sequenced along with some flanking sequence. The mature protein is 86 amino acids in length and contains four covalently bound haem groups, with a molecular weight of 11780 Da. The electronic absorption spectrum is characteristic of a low-spin c-type cytochrome with an α-peak at 551nm. A redox titration of the four haems, yielded of values at -60 mV and -200 mV, within the range observed for cytochromes c3. Resonance Raman spectra of the protein contain bands characteristic of low-spin haems, consistent with bis-histidine ligation for all haems. The deduced amino acid sequence from the cycA gene is 86 residues long for mature cytochrome c3 and has an additional 25 amino acid, periplasm directing presequence. The predicted sequence contains four, CXXCH haem binding motifs. This is consistent with the presence of four c-type haems in the mature protein. A total of eight histidines in the amino acid sequence is consistent with four bis-histidine ligated haems. Two additional reading frames, in the same orientation, lie on either side of the cycA gene. The reading frames show sequence similarly with two cytoplasmic proteins and are clearly unrelated to cytochrome c3. Flavocytochrome b2 (L-lactate : cytochrome c oxidoreductase (E. C. is a homotetrameric enzyme from the mitochondria of Saccharomyces cerevisiae. Each monomer consists of an N-terminal cytochrome domain and a C-terminal flavin domain, joined by a short flexible peptide. The haem domain has been identified as being mobile from the crystal structure of the Saccharomyces cerevisiae enzyme and a nuclear magnetic resonance study of Hansenula anomala flavocytochrome b2. The rate of flavin to haem electron transfer observed in the wild-type enzyme is ˜ 1500 s-1. This rate has is lower than expected considering the distance between the cofactors is ˜10Å.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available