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Title: Studies of cytoplasmically inherited genes for components of the mitochondrial ATPase complex : analysis of the Oli-2 region of the mitochondrial genome of Saccharomyces cerevisiae
Author: Ray, Malay Kumar
ISNI:       0000 0001 3509 6936
Awarding Body: University of Warwick
Current Institution: University of Warwick
Date of Award: 1985
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This thesis describes studies of the structure and organisation of the Oli-2 region of the mitochondrial genome from wild type, drug resistant (01i2 . Ossl ) and mit strains of the yeast Saccharomyces cercvisiac . In addition attempts have been made to identify the locus of cytoplasmic, nonmitochondrial markers (VENR , TET R, Rh8GR), to drugs which affect mitochondrial energy metabolism. Firstly, a fine structure genetic map of the Oli-2 region of the mitochondrial genome has been generated by petite deletion mapping. Two mit mutations (pho8 and pho9) have been mapped upstream and one mit mutation (mit-175) has been mapped downstream of the 01i2 locus (Chapter-2). A problem was identified regarding the effect of a nuclear gene ( kar-1) on the copy number and transmission of petite (p ) mitochondrial genomes I Chapter-3). To circumvent this problem the relevent portions of the mitochondrial DNA l mt-DNA) from various mutants of the Oli-2 region have been cloned in a multicopy plasmid. pAT 153 of E. colI, for their amplification and propagation (Chapter-4). The cloned DMAs have been sequenced using the single stranded phage, M 13 as a sequencing vector. A sequence of about 4000 bp. starting from the Carboxyl terminal end of cytochrome oxidase subunit-1 (Oxi-3) to 1500 bp downstream of 01i2 has been sequenced. Three main reading frames have been identified in this stretch of the DNA segment. The mutations (0/i'2 , Oa 1 ) leading to the resistivity towards the drugs oli- gomycin and ossamycin have been located in the reading frame for subunit-6. The mit mutation (pho9) has been found not to lie on the structural gene for subunit-8 which is located upstream of the gene for subunit-6. It is assumed that the mutation is possibly located in the intergenic regulatory region of the genes. A putative reading frame has been identified downstream of subunit-6 reading frame, which could be the possible site for the genetic locus, mit-175 (Chapter-5). Models for the secondary and tertiary structures of subunit-6, subunit-8, and subunit-9 have been proposed on a theoretical basis using hydrophobicity plots and a modified Chou and Fasman method (Chou & Fasman, 1978). Suggestions as to the mechanism of inhibi­tion of oxidative phosphorylation by oligomycin and ossamycin have been made on the basis of these models. The present studies also indicate that subunit-8 has structural analogies to subunit-b of E. colt ATP synthetase (Chapter-6). An attempt has also been made to identify a cytoplasmic candidate for nonmitochondrial, cytoplasmic genetic markers (P£,VR, TETR, Rh6GR) with special emphasis on studies of the 3 μ plasmid (Chapter-7). It has been demonstrated that the 2μ plasmid, or dsRNAs found in the cytoplasm are not the bearer of these genetic markers. In spite of the fact that the 3 μ DNA species under investigation has an insertion, no evidence has been obtained that the 3 μ plasmid contain the above markers. The existence of a high molec­ular weight plasmid in the cytoplasm of S. cercvisiae has also been demonstrated.
Supervisor: Not available Sponsor: West Bengal (India)
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: QP Physiology