分子生物学第八章蛋白质定位Proteinlocalization.ppt
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1、Chapter 8Protein localization8.1 Introduction8.2 Chaperones may be required for protein folding8.3 Post-translational membrane insertion depends on leader sequences 8.4 A hierarchy of sequences determines location within organelles 8.5 Signal sequences initiate translocation 8.6 How do proteins ente
2、r and leave membranes? 8.7 Anchor signals are needed for membrane residence 8.8 Bacteria use both co-translational and post-translational translocation 8.9 Pores are used for nuclear ingress and egress 8.10 Protein degradation by proteasomesLeader of a protein is a short N-terminal sequence responsi
3、ble for passage into or through a membrane.8.1 IntroductionFigure 8.1 Overview: proteins that are localized post-translationally are released into the cytosol after synthesis on free ribosomes. Some have signals for targeting to organelles such as the nucleus or mitochondria. Proteins that are local
4、ized cotranslationally associate with the ER membrane during synthesis, so their ribosomes are membrane-bound. The proteins pass into the endoplasmic reticulum, along to the Golgi, and then through the plasma membrane, unless they have signals that cause retention at one of the steps on the pathway.
5、 They may also be directed to other organelles, such as endosomes or lysosomes.8.1 IntroductionFigure 8.2 Proteins synthesized on free ribosomes in the cytosol are directed after their release to specific destinations by short signal motifs.8.1 IntroductionFigure 8.3 Membrane-bound ribosomes have pr
6、oteins with N-terminal sequences that enter the ER during synthesis. The proteins may flow through to the plasma membrane or may be diverted to other destinations by specific signals.8.1 IntroductionFigure 8.4 A protein is constrained to a narrow passage as it crosses a membrane. 8.2 Chaperones 8.2
7、Chaperones may be required may be required for protein foldingfor protein folding Figure 8.5 Chaperone families have eukaryotic and bacterial counterparts (named in parentheses). 8.2 Chaperones may be required for protein folding8.2 Chaperones may be required for protein folding Figure 8.6 DnaJ assi
8、sts the binding of DnaK (Hsp70), which assists the folding of nascent proteins. ATP hydrolysis drives conformational change. GrpE displaces the ADP; this causes the chaperones to be released. Multiple cycles of association and dissociation may occur during the folding of a substrate protein. 8.3 The
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- 分子生物学 第八 蛋白质 定位 Proteinlocalization