清华大学：《分子生物学》（英文版）Chapter 8 Protein localization

Chapter 8 Protein localization 莘大

Chapter 8 Protein localization

8.1 Introduction 8. 2 Chaperones may be required for protein folding 8.3 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 enter 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 proteasomes 消当

8.1 Introduction 8.2 Chaperones may be required for protein folding 8.3 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 enter 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 proteasomes

8.1 Introduction Leader of a protein is a short N-terminal sequence responsible for passage into or through a membrane 消当

Leader of a protein is a short N-terminal sequence responsible for passage into or through a membrane. 8.1 Introduction

8.1 Introduction Secreted protein Figure 8. 1 Overview: proteins that are localized post-translationally are sma membrane prote in released into the cytosol after synthesis on free ribosomes. Some have signalS a Coated vesicle transport for targeting to organelles such as th nucleus or mitochondria. Proteins that are localized cotranslationally associate -gOLgi retention signal Cytosolic with the Er membrane during synthesis proteins WER retention signal so their ribosomes are " membrane M itochondrial signa bound". The proteins pass into the ■■■I endoplasmic reticulum, along to the Golgi, and then through the plasma Free" ribosome Membranous membrane, unless they have signals that bosomed cause retention at one of the steps on the pathway. They may also be directed Nuclear signal to other organelles, such as endosomes or lysosomes 请莘大 I Post-translational transport Co-translational transport E:a

Figure 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 localized 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. They may also be directed to other organelles, such as endosomes or lysosomes. 8.1 Introduction

8.1 Introduction ↓ Organelle Signal Type Signal location length Mito chondron N-terminal Amphipathic helix 12-30 Chloroplast N-terminal Charge >25 Nucleus nternal Bas r partite 7-9 Figure 8.2 Proteins synthesized on free ribosomes in the cytosol are directed after their release to specific destinations by short signal motifs 消当

Figure 8.2 Proteins synthesized on free ribosomes in the cytosol are directed after their release to specific destinations by short signal motifs. 8.1 Introduction

Plasma membrane 8.1Introduction y00me■G0g Mannose-6-phosphate C-terminal KDEL Figure 8.3 Membrane-bound ribosomes have proteins with N-terminal sequences N-teminal signal that enter the er during sequence is cleaved synthesis. The proteins may Endoplasmic reticulum flow through to the plasma membrane or may be Cytosol diverted to other destinations by specific signals 消当

Figure 8.3 Membrane-bound ribosomes have proteins 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 Introduction

8.2 Chaperones may be required Protein acquires confomation after for protein folding membrane passage Protein must pass through channel in membrane Figure 8.4 a protein is constrained to a Folded conform ation narrow passage as it could prevent passage through membrane crosses a membrane 消当

Figure 8.4 A protein is constrained to a narrow passage as it crosses a membrane. 8.2 Chaperones may be required for protein folding

8.2 Chaperones may be required for protein folding System Function HSp70 H sp70(Dnak) ATPase H sp40(DnaJ) stimulates ATPase GrpE (GrpE) Nucleotide exchange factor Chaperonin H sp60(GroEL)Foms two heptameric rings Hsp10 (GroES)Foms cap Figure 8.5 Chaperone families have eukaryotic and bacterial counterparts(named in parentheses) 消当

Figure 8.5 Chaperone families have eukaryotic and bacterial counterparts (named in parentheses). 8.2 Chaperones may be required for protein folding

8.3 The Hsp70 family is ubiquitous rpE ATP ATP→ ADP EtADP DnaJ DnaK 甲■ ycle is repeated Figure 8.6 Dnaj assists 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 消当

Figure 8.6 DnaJ assists 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 Hsp70 family is ubiquitous

8.4 Hsp60/GroEL Pr otein enters throu gh forms an end of cylinder oligomeric ring structure Figure 8.7-IA protein may sequestered within a controlled environment for folding or Protein in tracts only degradation with walls of cavity 消当

Figure 8.7-1 A protein may be sequestered within a controlled environment for folding or degradation. 8.4 Hsp60/GroEL forms an oligomeric ring structure