▁further ▁from ▁the ▁more ▁polar ▁catal yt ic ▁loop . ▁Comp ared ▁to ▁ATP ' s ▁tri ph osph ates , ▁accommod ating ▁bal an ol ' s ▁ben z oph en one ▁rings ▁indu ces ▁the ▁re arr ang ement ▁of ▁catal yt ic ▁side - ch ains ▁P he 5 4 ▁and ▁Ser 5 3 , ▁en abling ▁favor able ▁polar ▁and ▁non pol ar ▁interactions ▁and ▁likely ▁contrib uting ▁to ▁bal an ol ' s ▁pot ent ▁in hib itory ▁effect ▁on ▁these ▁kin ases . ▁ ▁Action ▁against ▁other ▁protein ▁kin ases ▁ ▁As ▁bal an ol ▁acts ▁specifically ▁at ▁the ▁ATP - binding ▁site ▁in ▁the ▁catal yt ic ▁core ▁of ▁PK A ▁and ▁PK C , ▁it ▁was ▁initially ▁hypoth es ized ▁that ▁bal an ol ▁could ▁in hib it ▁all ▁ser ine / th re on ine ▁kin ases ▁sharing ▁a ▁conser ved ▁ATP - binding ▁site . ▁However , ▁bal an ol ▁does ▁not ▁in hib it ▁all ▁ser ine / th re on ine ▁kin ases ▁uniformly . ▁Aff inity ▁to ▁bal an ol ▁var ies ▁greatly ▁( K i ▁= ▁ 1 . 6 ▁– ▁ 7 4 2 ▁n M ), ▁with ▁several ▁members ▁of ▁the ▁ser ine / th re on ine ▁protein ▁kin ase ▁family ▁not ▁being ▁affected ▁at ▁all , ▁even ▁though ▁aff inity ▁of ▁these ▁kin ases ▁to ▁ATP ▁var ies ▁little ▁( 1 3 - 6 0 ▁ μ M ). ▁Bal an ol ▁exhib its ▁the