SUMMARY: The aim of this work was to determine the extent to which the periplasmic cytochromes and blue copper proteins could replace each other during growth of an obligate methylotroph (organism 4025) on methanol and methylamine. This was done by varying the relative concentrations of these proteins as a result of varying the amount of copper added to the growth medium during growth in oxygen-limited conditions. It was shown that the amount of added copper required for maximum growth was greater during growth on methylamine than on methanol. The concentrations of membrane-bound cytochromes and were not markedly affected by the copper concentration added to the growth medium whereas the concentrations of soluble cytochromes and blue copper proteins varied considerably. The concentrations of cytochrome were highest at the copper concentrations giving maximum growth; this was more obvious during growth on methanol (when this cytochrome has a specific function) than on methylamine. The concentrations of blue copper proteins were highest at the copper concentrations which supported maximum growth (except for the absence of amicyanin during growth on methanol). In the absence of added copper, amicyanin could not be detected, and in the absence of added iron neither amicyanin nor ‘azurin’ was detectable. The most important conclusions are that high concentrations of amicyanin may not be essential for methylamine oxidation, that ‘azurin’ may replace cytochrome for some electron-transport functions, and that iron is required for synthesis of blue copper proteins.


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