Methylamine oxidation in methylotrophic bacteria
Methylamine oxidation in methylotrophic bacteria
This thesis investigates the electron transport chain present in methylotrophic bacteria during growth on methylamine. The majority of experiments have been performed using two organisms, the facultative methylotroph, Pseudomonas AM1 and the obligate methylotroph organism 4025. Methylamine-grown Pseudomonas AM1 possessed a blue copper protein, amicyanin, which was an efficient electron acceptor from methylamine dehydrogenase. Amicyanin is a small, basic protein which has a mid-point redox potential of 269mV and an absorbance maximum at 596nm. No other blue copper protein was observed in Pseudomonas AM1. A mutant of Pseudomonas AM1, mutant PCT76, grown on succinate in the presence or absence of methylamine contained a second blue copper protein, azurin. This was a small, basic protein with absorbance maxima at 450, 592 and 750nm. Organism 4025, when grown on methylamine contained only b-type and c-type cytochromes. In the absence of any a-type cytochrome it was concluded that respiration in these bacteria is catalysed entirely by way of the CO-binding cytochrome b (cytochrome o). The soluble fraction of organism 4025 contained cytochrome cH (34% of total) and cytochrome cL (66% of total). The concentration of soluble cytochrome c was greater (about 3-fold) after growth on methanol, cytochrome cL being increased 1.5-fold and cytochrome cH being increased about 6.5-fold compared with concentrations after growth on methylamine. Organism 4025, grown on methanol or methylamine, contained a blue copper protein, azurin, which was unable to function as an electron acceptor from the methylamine dehydrogenase of the same organism. The azurin was a small, basic protein with a mid-point redox potential of 323mV. During growth on methylamine a second blue copper protein, amicyanin (94% of total) was observed in organism 4025. The amicyanin was a small, acidic protein with a mid-point redox potential of 294mV which was demonstrated to be an efficient electron acceptor from the methylamine dehydrogenase isolated from organism 4025. The methylamine dehydrogenase, cytochromes cH and cL, amicyanin and azurin from methylamine-grown organism 4025 were purified and characterised, and, were all shown to be located in the periplasmic space. The most important contribution of this thesis is the demonstration that the primary electron acceptor for electrons derived from the oxidation of methylamine by methylamine dehydrogenase in facultative and obligate methylotrophs is a blue copper protein, amicyanin. (D68302/86)
University of Southampton
1985
Lawton, Stephen Ashley
(1985)
Methylamine oxidation in methylotrophic bacteria.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
This thesis investigates the electron transport chain present in methylotrophic bacteria during growth on methylamine. The majority of experiments have been performed using two organisms, the facultative methylotroph, Pseudomonas AM1 and the obligate methylotroph organism 4025. Methylamine-grown Pseudomonas AM1 possessed a blue copper protein, amicyanin, which was an efficient electron acceptor from methylamine dehydrogenase. Amicyanin is a small, basic protein which has a mid-point redox potential of 269mV and an absorbance maximum at 596nm. No other blue copper protein was observed in Pseudomonas AM1. A mutant of Pseudomonas AM1, mutant PCT76, grown on succinate in the presence or absence of methylamine contained a second blue copper protein, azurin. This was a small, basic protein with absorbance maxima at 450, 592 and 750nm. Organism 4025, when grown on methylamine contained only b-type and c-type cytochromes. In the absence of any a-type cytochrome it was concluded that respiration in these bacteria is catalysed entirely by way of the CO-binding cytochrome b (cytochrome o). The soluble fraction of organism 4025 contained cytochrome cH (34% of total) and cytochrome cL (66% of total). The concentration of soluble cytochrome c was greater (about 3-fold) after growth on methanol, cytochrome cL being increased 1.5-fold and cytochrome cH being increased about 6.5-fold compared with concentrations after growth on methylamine. Organism 4025, grown on methanol or methylamine, contained a blue copper protein, azurin, which was unable to function as an electron acceptor from the methylamine dehydrogenase of the same organism. The azurin was a small, basic protein with a mid-point redox potential of 323mV. During growth on methylamine a second blue copper protein, amicyanin (94% of total) was observed in organism 4025. The amicyanin was a small, acidic protein with a mid-point redox potential of 294mV which was demonstrated to be an efficient electron acceptor from the methylamine dehydrogenase isolated from organism 4025. The methylamine dehydrogenase, cytochromes cH and cL, amicyanin and azurin from methylamine-grown organism 4025 were purified and characterised, and, were all shown to be located in the periplasmic space. The most important contribution of this thesis is the demonstration that the primary electron acceptor for electrons derived from the oxidation of methylamine by methylamine dehydrogenase in facultative and obligate methylotrophs is a blue copper protein, amicyanin. (D68302/86)
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Published date: 1985
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Local EPrints ID: 461694
URI: http://eprints.soton.ac.uk/id/eprint/461694
PURE UUID: 4025c953-e11f-40ed-9a51-1b2df376e15d
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Date deposited: 04 Jul 2022 18:52
Last modified: 04 Jul 2022 18:52
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Author:
Stephen Ashley Lawton
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