Three-dimensional structures of cyclins showing the location of conserved and variable secondary structure elements. A, human cyclin A1-CDK2 complex; B, human B1 cyclin; C, yeast B1 cyclin; D human B3 cyclin; E human cyclin D1-CDK4 complex; F, human E1 cyclin. Secondary structures: replacement number significantly greater than expected is marked "+". CDK molecules are in red; cyclin regions within gapless alignment are in blue.
Gunbin et al. BMC Evolutionary Biology 2011 11:224 doi:10.1186/1471-2148-11-224