A. Chestukhin et al., FUNCTIONAL MALLEABILITY OF THE CARBOXYL-TERMINAL TAIL IN PROTEIN-KINASE-A, The Journal of biological chemistry, 271(17), 1996, pp. 10175-10182
The catalytic (C) subunit of protein kinase A (PKA) is regarded as a f
ramework for the protein kinase family. Its sequence is composed of a
conserved core (residues 40-300) between two segments at the amino and
carboxyl termini of the protein. Since the various protein kinases di
ffer in their specificity, it seems reasonable to assume that these no
nhomologous segments may be involved in endowing each kinase with its
individual specificity. Here we present data to show that the cluster
of acidic amino acids ((328)DDYEEEE(334)) at the carboxyl-terminal ''t
ail'' of the C subunit, specifically Tyr(330), contributes to its subs
trate recognition. This is based on three complementary lines of evide
nce: (i) on a conformation-sensitive cleavage of the C subunit by a ki
nase-splitting membranal proteinase that specifically recognizes this
cluster, to demonstrate the occurrence in solution of ''open'' (cleava
ble) and ''closed'' (noncleavable) conformations of the C subunit; (ii
) on analysis of the three-dimensional structures of the open and clos
ed conformations of the C subunit, showing an similar to 7-Angstrom mo
vement of the phenolic hydroxyl of Tyr(330) to reach (in the closed co
nformation) an similar to 3-Angstrom distance from the nitrogen atoms
of the Arg residue at position p-3 of the PKA consensus sequence; and
(iii) on single-site mutations of the C subunit (e.g. Y330A) that show
a significant contribution of Tyr(330) to the K-m of PKA for its subs
trates/inhibitors and to its catalytic efficacy (V-max/K-m).