Subdomain VIB of Cyclin-Dependent Kinase2

Subdomain VIB comprises residues 122-139 which make up beta-6, L10, beta-7, and L11. Beta strands 6 and 7 are hydrophobic. The region between them is the catalytic loop of the molecule which contains the consensus motif, HRDLKxxN. It is called the catalytic loop because it is thought that Asp127 is responsible for the catalytic activity that drove the nucleophilic attack by the hydroxyl oxygen on the gamma phosphate of ATP. Asn132, along with Asp145 from subdomain VII and a water molecule, contributes to the coordination of Mg2+. Asp127, Lys129, and Asn132 are highly conserved residues throughout the kinases, and are involved in positioning of ATP.