Question 1

Como é que as proteínas com pré-sequências entram na matriz mitocondrial?

Accepted Answer

As proteínas que carregam presequências são enfiadas através do complexo TOM/TIM. A Hsp70 mitocondrial liga-se ao peptídeo à medida que sai do canal TIM e move-o into the into the into the into the into the into the into the into the into the into the into the into the into the into the into the into the into the into the into the into the into the into the into the into the into the into the into the into the into the into the into the into the into the into the into the into the into the into the into the into the into the into the into the into the into the into the into the into the into the into the into the into the into the into the into the into the into the into the into the into the into the into the into the into the into the into the into the into the into the into the into the into the into the into the into the into the into the into the into the into the into the into the into the into the into the into the into the into the into the into the into the into the into the into the into the into the into the into the into the into the into the into the 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As proteases da matriz então clivam a presequência, libertando a proteína ativa. Este mecanismo assegura a direcionamento e processamento adequados das proteínas destinadas à matriz.

Question 2

Que papel a Mia40 desempenha na importação de proteínas do espaço intermembranar?

Accepted Answer

Mia40 é uma oxidoredutase que importa proteínas do espaço intermembranar sem presequências. A forma oxidada da Mia40 forma uma ligação dissulfeto transitória com resíduos de cisteína no polipeptídeo que está a entrar e puxa o peptídeo nascente através do canal TOM. Uma vez que todo o peptídeo é enfiado através, a Mia40 é reduzida e reciclada para outro ciclo de importação.

Question 3

Como fazem as sequências de transferência de parada direcionar proteínas para a membrana mitocondrial interna?

Accepted Answer

Proteínas da membrana interna com sequências de parada-transferência são detidas durante a translocação através do complexo TIM e inseridas diretamente na membrana. Este mecanismo impede a translocação completa para a matriz. Algumas dessas proteínas são primeiro processadas por sinal peptidases antes da inserção, enquanto outras são reconhecidas pela translocase OXA, que as incorpora na membrana.

Question 4

O que distingue os dois caminhos para a classificação de proteínas da membrana interna?

Accepted Answer

O caminho de parada-transferência prende precursores com segmentos hidrofóbicos internos dentro do canal TIM e os libera lateralmente na o interior membrana. O caminho conservador transloca precursores completamente na matriz primeiro, então os monta na membrana via proteína OXA. Proteases da matriz clivam pré-sequências na rota conservadora antes das proteínas se dobrarem usando energia da chaperonina.

Question 5

Como é que Erv1 coopera com Mia40 na via MIA?

Accepted Answer

Erv1 é uma oxidoredutase dependente de flavina que coopera com Mia40 para oxidar resíduos de cisteína precursora, facilitando o dobramento e transporte no espaço intermembrana. Erv1 transfere elétrons para o motivo CPC reduzido de Mia40 via citocromo C e a cadeia respiratória. Este ciclo redox regenera Mia40 oxidado para rodadas subsequentes de importação de proteínas.

Question 6

O que acontece com as proteínas da matriz após serem translocadas?

Accepted Answer

As proteínas da matriz são clivadas por peptidases de processamento da matriz após a translocação através do TIM23. Alguns precursores passam por processamento adicional pela peptidase intermediária mitocondrial ou pela protease da membrana interna I em locais adicionais de clivagem de pré-sequência. As proteínas da matriz processadas são então liberadas na matriz onde as chaperoninas as dobram usando energia de hidrólise de ATP.

Question 7

Como as sinal peptidases regulam a localização da proteína do espaço intermembranar?

Accepted Answer

As proteínas do espaço intermembranar carregam um sequência sinal hidrofóbico adicional que impede a translocação através do complexo TIM. As sinal peptidases clivam este segmento hidrofóbico, liberando a proteína ativa no espaço intermembranar. Este mecanismo de clivagem assegura que as proteínas permaneçam no espaço intermembranar em vez de continuar na matriz.

Translocação de Proteínas para as Mitocôndrias

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