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Title: Respiratory enzymes from Shewanella MR-1
Author: Atanasiu, Doina
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 2001
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Shewanella MR-1 is a Gram-negative, facultatively anaerobic bacterium isolated from Lake Oneida, New York. It can couple its anaerobic growth to the reduction of a wide variety of compounds such as nitrate, nitrite, TMAO, DMSO, fumarate, manganese(IV) and iron(III) oxides, sulfite and thiosulfate. Analysis of the genome sequence reveals the presence of a large number of respiratory enzymes. Three of these proteins were selected for further study: a decaheme cytochrome c, a heptaheme cytpchrome c and a flavoprotein. Decaheme 129 (Cyc129) is 37% similar to MtrC, a decaheme protein from the same organisms that have been shown to be involved in iron(III) and manganese(IV) respiration. The DNA sequence indicated the presence of a lipoprotein signal sequence but the protein is loosely associated to the membrane. Compared to the wild-type strain, no phenotypic differences were noted when the cyc129 gene was disrupted by the insertion of an antibiotic cassette. The second protein, heptaheme 202 (Cyc202) is a soluble, periplasmic protein and is the only heptaheme cytochrome c in Shewanella MR-1. Phenotypic studies indicate that it might be involved in the electron transport to the outer-membrane located iron-manganese reductases. FccA56 is similar to the flavin domain of flavocytochrome c3 , the fumarate reductase from Shewanella MR-1. The gene encoding this protein is part of a cluster that also encodes a tetraheme c-type cytochrome and a histidine ammonia lyase-like protein. Substitution of the highly conserved amino acids involved in substrate binding suggests that fumarate is not the physiological substrate of FcA56, but has a similar substrate that contains only one carboxylic group. The protein was purified after overexpression in E. coli. A UV-visible absorption spectrum confirmed that the ~52 kDa protein has absorption maxima at 450 and 380 nm, characteristic for flavoproteins.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available