Control of the synthesis, activity, and turnover of enzymes of sulfur metabolism in Neurospora crassa

The synthesis of aryl sulfatase, choline-O-sulfate permease, and two distinct sulfate permeases are repressed by methionine, but the activity of these enzymes is not subject to feedback inhibition. The permease species, but not aryl sulfatase, are also regulated by dynamic turnover, displaying a functional half-life of approximately 2 hr. The rate of turnover of these permeases is not influenced by the presence of the end product, methionine. Development of sulfate permease activity occurs only by de novo synthesis which requires both a lifting of methionine repression and a functional cys-3 product. The turnover system for sulfate permease is not present in dormant conidia but appears to be synthesized relatively rapidly during germination. Preexisting conidial sulfate permease is lost by turnover during germination and outgrowth into the mycelial phase, during which both permease species are synthesized anew, although the high affinity system contributes most of the total activity in growing mycelia.