To understand the structural basis for the different catalytic behaviour of the flavocytochromes b2 from Saccharomyces cerevisiae and Hansenula anomala we have cloned and sequenced the gene encoding the latter. We have compared the amino acid sequences of the mature proteins in the context of the known crystal structure of S. cerevisiae flavocytochrome b2. Overall there is 60% sequence identity, but two surface loops in particular are strikingly different in primary structure and net charge.

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