Subdomain V of Kinase Domain of Protein Kinase A

Subdomain V acts as a bridge between the large and small lobes of protein kinase A, but it also helps in catalysis. The subdomain consists of a hydrophobic beta strand (5) present in the small lobe and a small alpha helix present in the large lobe (D), and the chain that connects them.


Hydrophobicity profile of Protein Kinase A with beta strand 5 in green

The chain that spans between the beta strand and the alpha helix contains Glu121, Val123 and Glu 127 help to anchor the MgATP by hydrogen bonding with the adenine or ribose rings. The residues Met120, Tyr122 and Val123 contribute to a hydrophobic pocket that surrounds the adenine ring.
Hydrophobicity profile showing pocket formed by Met120, Tyr122 & Val123

The Glu 127 also participates in the binding of the pseudosubstrate synthetic inhibitor, by forming a peptide bond with an Arg in the inhibitor. This Arg represents the first Arg in the PKA substrate recoginition consensus of Arg-Arg-X-Ser-hydrophobic