Chapter 5.5 Protein sorting. The Structure of Proteins.
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Proteins consist of one or more polypeptide chains. A polypeptide consists of a series of amino acids joined ny peptide bonds. These chains are folded in a very precise fashion and if this folding is abolished than the protein generally becomes non-functional.
Typically the three dimensional structure of a protein is composed of a series of fairly rigid sections strongly stabilised by hydrogen bonds (mainly alpha-helix and beta pleated sheet) and flexible zones.
The flexibility means that a molecule binding at one point on the surface of the protein will produce sympathetic changes at other points, in particular in the sites which bind the substrate and catalyse the reaction.
1 signal peptide
exist in N-protein
16-26 aa,including hydrophobic center, N-protein and C-protein
Synthesis and transport occurred at the same time
Start transfer sequence:
lead peptide go through ER
Stop transfer sequence:
after protein synthesised in the cytosol,then transferd to organelle,so refered post translocation
In the process of protein transmembrane,need ATP to get rid of fold ,and some proteins to help to fold functional proteins
是内质网膜上的一种停泊蛋白(docking protein, DP)，即是一种膜的整合蛋白，暴露在胞液面，一旦它与SRP-核蛋白体复合物结合，SRP即被释放，翻译开始并通过内质网膜上的转移器，转移生长的多肽链横过膜
polypeptide completed synthesis in the cytosol,and then transfer into orther organelle
1 Signal peptide
2 ER Retrivieval signal(KDEL)
3 Leader peptide for mitochondria
4 Nucleus location signal
A Gridding protein coated vesicles网格蛋白有被小泡
B COPⅡ coated vesicles ：ER—Golgi
C COPⅡ coated vesicles
retrieve escaped proteins---ER
cavity of transmembrane ER protein combine with soluble protein of cavity ER
1 Double direction transport
Retrograde transport from Golgi to ER; anterograde transport from ER to Golgi ;
2 Main function was callback escaped protein from golgi to ER,
3 Retrieval signal（Lys-asp-glu-leu,or KDEL）, golgi CGN can recognize retrieval signal,form COPⅠ coated vesicles to transfort to ER ,If protein was short of retrieval,protein cannot come back to ER
4 ER is Open prison
Maily located in cis golgi network and ER-to GOLGI trasport vesicle
Chief function is bing proteinwith KDELand return them to ER
1 Selective fusion is the key factor for directional protein trasport.vesicle from ER only fused with cis CGN(高尔基体管网区)
2 Rough ER is material source ,and golgi is important distributing center
3 ER is Open prison