Protein targeting secretory proteins

Secretory proteins have an N-terminal signal peptide which targets the protein to be synthesized on the rough endoplasmic reticulum (RER). During synthesis it is translocated through the RER membrane into the lumen. Vesicles then bud off from the RER and carry the protein to the Golgi complex, where it becomes glycosylated. Other vesicles then carry it to the plasma membrane. Fusion of these transport vesicles with the plasma membrane then releases the protein to the cell exterior. 

A growing body of evidence indicates that in addition to a targeting element, membrane translocation also requires that the secretory protein assumes a loosely folded or translocation-competent state. The focus of this review is the role that SecB and other molecular chaperones play in sponsoring efficient protein secretion in E. coli. 

Figure 11.24. Golgi Complex as Sorting Center. The Golgi complex is the sorting center in the targeting of proteins to lysosomes, secretory vesicles, and the plasma membrane. The cis face of the Golgi complex receives vesicles from the ER, and the trans face sends a different set of vesicles to target sites. Vesicles also transfer proteins from one compartment of the Golgi complex to another. [Courtesy of Dr. Marilyn Farquhar.]...

Parmer RJ, Xi XP, Wu HJ, ef al. (1993) Secretory protein traffic. Chromogranin A contains a dominant targeting signal for the regulated pathway. In J. Clin. Invest. 92 1042-54. 

Tonkin, C. J., Pearce, J. A., McFadden, G. I., and Cowman, A. F. (2006). Protein targeting to destinations of the secretory pathway in the malaria parasite Plasmodium falciparum. Curr. Opin. Microbiol. 9,381-387. 

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