RESUMO
Microtubule (MT)-destabilizing kinesin 13s perform fundamental roles throughout the cell cycle. In this study, we show that the Drosophila melanogaster kinesin 13, KLP10A, is phosphorylated in vivo at a conserved serine (S573) positioned within the alpha-helix 5 of the motor domain. In vitro, a phosphomimic KLP10A S573E mutant displays a reduced capacity to depolymerize MTs but normal affinity for the MT lattice. In cells, replacement of endogenous KLP10A with KLP10A S573E dampens MT plus end dynamics throughout the cell cycle, whereas a nonphosphorylatable S573A mutant apparently enhances activity during mitosis. Electron microscopy suggests that KLP10A S573 phosphorylation alters its association with the MT lattice, whereas molecular dynamics simulations reveal how KLP10A phosphorylation can alter the kinesin-MT interface without changing important structural features within the motor's core. Finally, we identify casein kinase 1alpha as a possible candidate for KLP10A phosphorylation. We propose a model in which phosphorylation of the KLP10A motor domain provides a regulatory switch controlling the time and place of MT depolymerization.
Assuntos
Proteínas de Drosophila/metabolismo , Drosophila melanogaster/metabolismo , Cinesinas/metabolismo , Microtúbulos/metabolismo , Sequência de Aminoácidos , Animais , Caseína Quinase Ialfa/genética , Caseína Quinase Ialfa/metabolismo , Linhagem Celular , Proteínas de Drosophila/química , Proteínas de Drosophila/genética , Cinesinas/química , Cinesinas/genética , Modelos Moleculares , Dados de Sequência Molecular , Fosforilação , Isoformas de Proteínas/genética , Isoformas de Proteínas/metabolismo , Estrutura Terciária de Proteína , Interferência de RNA , Proteínas Recombinantes de Fusão/genética , Proteínas Recombinantes de Fusão/metabolismo , Alinhamento de Sequência , Tubulina (Proteína)/química , Tubulina (Proteína)/genética , Tubulina (Proteína)/metabolismoRESUMO
After infecting the Vero E6 cells by nasal/throat swabs collected from SARS patients, we studied the SARS-associated virus by electron microscopy and molecular biological technique. The results show that the diameter of newly isolated virus is about 50 nm without envelope or 100 nm with envelope. The virus was proved to be a new coronavirus by RT-PCR and it responded positively to convalescent-phase serum specimen from SARS patients, which is the evidence that this new virus is etiologically linked to the outbreak of SARS. The morphogenesis and distribution of the virus are also discussed in this article.
