Classity the given mutations in the R or C subunit of cAMP$-$dependent protein kinase $($PKA$)$ based on whether they would lead to a constantly active PKA or a constantly inactive PKA.$$ MacmilConstantly active PKAConstantly inactive PKAAnswer BankA mutant R subunit cannot enter the substrate$-$binding cleft of the C subunit.A mutant R subunit cannot bind cAMP.A mutant C subunit cannot bind ATP.A mutant C subunit has a substrate$-$binding cleft that does not accomodate the R subunit.