Control over nitrogenase activity is accomplished by which of the following?
a. atp serves as an allosteric activator
b. amp serves as an allosteric inhibitor
c. nh4+ prevents expression of the genes that encode nitrogenase
d. phosphorylation prevents activity
e. none of the above

C

Explanation:

Control over nitrogenase activity is accomplished by  NH4+ prevents expression of the genes that encode nitrogenas.

Nitrogenase synthesis in free-living N2-fixing bacteria is universally under repressor control by ammonia. This, however, is not

the case for rhizobia. A need for N2 as inducer apparently does not

exist.  The degree of ammonia repression is unusual in its strength.

Nitrogenase activity is at least 1O,OOO-fold lower in extracts of

NH4+-grown cells versus N2-grown cells.

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