RESUMEN
The crystal structure of the cyclin D-dependent kinase Cdk6 bound to the p19 INK4d protein has been determined at 1.9 A resolution. The results provide the first structural information for a cyclin D-dependent protein kinase and show how the INK4 family of CDK inhibitors bind. The structure indicates that the conformational changes induced by p19INK4d inhibit both productive binding of ATP and the cyclin-induced rearrangement of the kinase from an inactive to an active conformation. The structure also shows how binding of an INK4 inhibitor would prevent binding of p27Kip1, resulting in its redistribution to other CDKs. Identification of the critical residues involved in the interaction explains how mutations in Cdk4 and p16INK4a result in loss of kinase inhibition and cancer.
Asunto(s)
Proteínas Portadoras/química , Proteínas de Ciclo Celular , Inhibidor p16 de la Quinasa Dependiente de Ciclina , Quinasas Ciclina-Dependientes , Proteínas Serina-Treonina Quinasas/química , Adenosina Trifosfato/metabolismo , Secuencia de Aminoácidos , Animales , Unión Competitiva , Proteínas Portadoras/metabolismo , Catálisis , Línea Celular , Cristalografía por Rayos X , Quinasa 6 Dependiente de la Ciclina , Inhibidor p19 de las Quinasas Dependientes de la Ciclina , Escherichia coli , Humanos , Insectos , Ratones , Datos de Secuencia Molecular , Conformación Proteica , Proteínas Serina-Treonina Quinasas/metabolismo , Proteínas Recombinantes/química , Proteínas Recombinantes/metabolismo , Homología de Secuencia de AminoácidoRESUMEN
In cancer, the biochemical pathways that are dominated by the two tumour-suppressor proteins, p53 and Rb, are the most frequently disrupted. Cyclin D-dependent kinases phosphorylate Rb to control its activity and they are, in turn, specifically inhibited by the Ink4 family of cyclin-dependent kinase inhibitors (CDKIs) which cause arrest at the G1 phase of the cell cycle. Mutations in Rb, cyclin D1, its catalytic subunit Cdk4, and the CDKI p16Ink4a, which alter the protein or its level of expression, are all strongly implicated in cancer. This suggests that the Rb 'pathway' is of particular importance. Here we report the structure of the p19Ink4d protein, determined by NMR spectroscopy. The structure indicates that most mutations to the p16Ink4a gene, which result in loss of function, are due to incorrectly folded and/or insoluble proteins. We propose a model for the interaction of Ink4 proteins with D-type cyclin-Cdk4/6 complexes that might provide a basis for the design of therapeutics against cancer. The sequences of the Ink4 family of CDKIs are highly conserved
Asunto(s)
Proteínas Portadoras/química , Proteínas de Ciclo Celular , Inhibidor p16 de la Quinasa Dependiente de Ciclina , Quinasas Ciclina-Dependientes/antagonistas & inhibidores , Conformación Proteica , Proteínas Proto-Oncogénicas , Secuencia de Aminoácidos , Animales , Ancirinas/química , Antineoplásicos/química , Antineoplásicos/farmacología , Proteínas Portadoras/genética , Proteínas Portadoras/farmacología , Ciclina D , Quinasa 4 Dependiente de la Ciclina , Inhibidor p19 de las Quinasas Dependientes de la Ciclina , Ciclinas/efectos de los fármacos , Diseño de Fármacos , Inhibidores Enzimáticos/química , Inhibidores Enzimáticos/farmacología , Humanos , Espectroscopía de Resonancia Magnética , Ratones , Modelos Moleculares , Datos de Secuencia Molecular , Mutación , Proteínas Recombinantes de Fusión/química , Proteínas Recombinantes de Fusión/genética , Homología de Secuencia de AminoácidoRESUMEN
We carried out a segregation analysis comparing the inheritance of collagen gene markers and joint hypermobility syndrome in two extended families. Our results exclude the genes encoding type III (COL3A1), type V alpha 2 chain (COL5A2) and type VI alpha 3 chain (COL6A3) unambiguously in both families. The simultaneous exclusion of both the type 1 alpha 1 and alpha 2 chain genes in the same family was not possible: COL1A1, but not COL1A2 was excluded in one and COL1A2, but not COL1A1 was excluded in the second. There was no suggestion of strong linkage to either of these loci. These data do not support the hypothesis that JHS in these families is caused by mutations in these collagen genes.
