Presenting your structures: the CCP4mg molecular-graphics software.

CCP4mg is a molecular-graphics program that is designed to give rapid access to both straightforward and complex static and dynamic representations of macromolecular structures. It has recently been updated with a new interface that provides more sophisticated atom-selection options and a wizard to facilitate the generation of complex scenes. These scenes may contain a mixture of coordinate-derived and abstract graphical objects, including text objects, arbitrary vectors, geometric objects and imported images, which can enhance a picture and eliminate the need for subsequent editing. Scene descriptions can be saved to file and transferred to other molecules. Here, the substantially enhanced version 2 of the program, with a new underlying GUI toolkit, is described. A built-in rendering module produces publication-quality images.

The structure of CDK4/cyclin D3 has implications for models of CDK activation.

Cyclin-dependent kinase 4 (CDK4)/cyclin D complexes are expressed early in the G(1) phase of the cell cycle and stimulate the expression of genes required for G(1) progression by phosphorylation of the product of the retinoblastoma gene, pRb. To elaborate the molecular pathway of CDK4 activation and substrate selection we have determined the structure of nonphosphorylated CDK4/cyclin D3. This structure of an authentic CDK/cyclin complex shows that cyclin binding may not be sufficient to drive the CDK active site toward an active conformation. Phosphorylated CDK4/cyclin D3 is active as a pRb kinase and is susceptible to inhibition by p27(Kip1). Unlike CDK2/cyclin A, CDK4/cyclin D3 can be inactivated by treatment with lambda-phosphatase, implying that phosphorylated T172 is accessible to a generic phosphatase while bound to a cyclin. Taken together, these results suggest that the structural mechanism of CDK4/cyclin D3 activation differs markedly from that of previously studied CDK/cyclin complexes.