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Title: Ribulose 1,5-bisphosphate carboxylase and carbon dioxide fixation in Rhodomicrobium vannielii (RM5) and Methylococcus capsulatus (Bath)
Author: Taylor, Stephen Colin
ISNI:       0000 0001 3514 6382
Awarding Body: University of Warwick
Current Institution: University of Warwick
Date of Award: 1979
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The ribulose 1 ,5-bisphosphate (RuBP) carboxylase of Rhodomicrobium vannielii (RM5) has been purified and its structure and properties investigated. The enzyme contains both catalyticalIy active large and regulatory small subunits although the small subunits are shown to be lost under certain conditions. Attention is drawn to the need for care in elucidating RuBP carboxylase quaternary structure, particularly where lengthy purification procedures are involved. The in vivo regulation of carbon dioxide fixation has been examined and found to differ in several respects to that reported for Rhodospirillum rubrum (Slater and Morris, 1973a, b), a physiologically similar organism but whose RuBP carboxylase lacks any small subunits (Tabita and McFadden, 1974a, b). The use of sucrose density gradient centrifugation in fixed angle rotors for RuBP carboxylase purification has been investigated and is shown to require short centrifugation times giving high resolution whilst allowing relatively large amounts of protein to be used per gradient. The advantages of this technique over gradients in swinging bucket rotors are discussed. The presence of RuBP carboxylase in extracts of methane grown Methylococcus capsulatus has been demonstrated, this being the first report of this enzyme in a methane oxidising bacterium. The importance of carbon dioxide fixation to M. capsulatus and the possible presence of a functioning Calvin cycl : has been investigated by enzyme and radiotracer studies and how RuBP carboxylase activity may be integrated into the overall metabolism of the cell, discussed. The RuBP carboxylase from M. capsulatus (Bath) has been purified and its structure and properties investigated. The enzyme has RuBP oxygenase activity and the metabolism of the product of this reaction, 2-phosphoglycol1 ate, is discussed with respect to its similarity to the serine pathway for one-carbon assimilation. The evolutionary link that M. capsulatus may represent between carbon dioxide and methane assimilating autotrophs is examined.
Supervisor: Not available Sponsor: British Petroleum Company
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: QD Chemistry ; QL Zoology ; QP Physiology ; QR Microbiology