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Title: Nitrogenase turnover in Gloeothece
Author: Dougherty, L. J.
Awarding Body: University College of Swansea
Current Institution: Swansea University
Date of Award: 1996
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Batch cultures of Gloeothece completely turnover both proteins of nitrogenase when grown under alternating light: darkness. The main aims of this study were to identify factors that may regulate the degradation of nitrogenase and to partially characterise the proteolytic enzyme(s) involved. Cultures of Gloeothece incubated under modified environments degraded the Fe-protein of nitrogenase at different rates. Catabolism of both proteins of Gloeothece nitrogenase was found to be under tight regulatory control, manifested at two levels. Firstly, changes in the intracellular concentration of a proteolytic enzyme(s) or a factor associated with it occur during growth under alternating light: darkness. However, there was no evidence that degradation of the Fe-protein may be enhanced by its ligation to any targeting protein. Secondly, fluctuations in the intracellular concentrations of metabolites may regulate proteolysis. The marked stimulation of degradation of nitrogenase by ATP suggests that, at least, the initial proteinase may be ATP-dependent. Preliminary studies suggest that photosynthesis may be down-regulated during the dark period of a diurnal cycle; and effect mediated by light and events in Photosystem II. Environments that increased the access of O2 to nitrogenase promoted modification of the Fe-protein in vivo. As yet the nature of modification is unknown, though glycosylation seems unlikely. Investigation using matrix-assisted laser desorption/ionization time of flight mass spectrometry highlighted the potential of this technique for the characterisation of posttranslational modifications and their location. Preliminary studies suggest a modifying group(s) with a total Mr of 2361.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available