title: Structural basis for CDK6 activation by a virus-encoded cyclin.
abstract: Cyclin from herpesvirus saimiri (Vcyclin) preferentially forms complexes with cyclin-dependent kinase 6 (CDK6) from primate host cells. These complexes show higher kinase activity than host cell CDKs in complex with cellular cyclins and are resistant to cyclin-dependent inhibitory proteins (CDKIs). The crystal structure of human CDK6--Vcyclin in an active state was determined to 3.1 A resolution to better understand the structural basis of CDK6 activation by viral cyclins. The unphosphorylated CDK6 in complex with Vcyclin has many features characteristic of cyclinA-activated, phosphorylated CDK2. There are, however, differences in the conformation at the tip of the T-loop and its interactions with Vcyclin. Residues in the N-terminal extension of Vcyclin wrap around the tip of the CDK6 T-loop and form a short beta-sheet with the T-loop backbone. These interactions lead to a 20% larger buried surface in the CDK6--Vcyclin interface than in the CDK2--cyclinA complex and are probably largely responsible for the specificity of Vcyclin for CDK6 and resistance of the complex to inhibition by INK-type CDKIs.
authors.affiliation: Physical Bioscience Division at E. O. Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
authors.forename: Ursula
authors.initials: U
authors.lastname: Schulze-Gahmen
authors.forename: Sung-Hou
authors.initials: SH
authors.lastname: Kim
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D018360:Crystallography, X-Ray; D051361:Cyclin-Dependent Kinase 6; D018844:Cyclin-Dependent Kinases; D016213:Cyclins / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000378:metabolism*; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006567:Herpesvirus 2, Saimiriine / Q000737:chemistry*; D006801:Humans; D006860:Hydrogen Bonding; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010766:Phosphorylation; D011485:Protein Binding; D011487:Protein Conformation; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry* / Q000378:metabolism*; D013329:Structure-Activity Relationship; D013379:Substrate Specificity; D014764:Viral Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000378:metabolism*
chemical_list: D016213:Cyclins; D004791:Enzyme Inhibitors; D014764:Viral Proteins; D017346:Protein Serine-Threonine Kinases; C495911:CDK6 protein, human; D051361:Cyclin-Dependent Kinase 6; D018844:Cyclin-Dependent Kinases