Coat proteins, recruitment

Vesicle budding is associated with coat proteins. What is the role of coat proteins in vesicle budding How are coat proteins recruited to membranes What kinds of molecules are likely to be Included or excluded from newly formed vesicles What is the best-known example of a protein likely to be Involved in vesicle pinching off ... 

Vesicles are transport containers that are formed upon recruitment of coat proteins from a donor membrane that fuse with an acceptor membrane. 

Step 2 Membrane-associated ARF recruits the coat proteins that comprise the coatomer shell from the cytosol, forming a coated bud. 

Toews AD, Barrett C, Morell P (1998) Monocyte chemoattractant protein 1 is responsible for macrophage recruitment following injury to sciatic nerve. J Neurosci Res 53 260-267 Toggas SM, MasUah E, Rockenstein EM, Rail GF, Abraham CR, Mucke L (1994) Central nervous system damage produced by expression of the HIV-1 coat protein gpl20 in transgenic mice. Nature 367 188-189... 

Further analysis of the cross-linked intermediate showed that lysine at position 250 of one capsid subunit was covalently linked to the identical amino acid on a second subunit. In a model of the nucleocapsid derived from both cryoelectron microscopy (cryo-EM) analysis and X-ray analysis of the nucleocapsid protein, the covalent bond connects a pentamer of coat proteins with a hexamer of coat proteins, that is, it is an intercapsomer contact rather than an intracapsomer contact. This finding was unexpected because a possible assembly model proposed preassembly of pentameric and hexameric units that would recruit RNA for assembly into the final structure. In light of the new data, however, this scenario is unlikely. Instead, the initial assembly intermediate appears to be a coat protein dimer bound to RNA and the dimer spans the intercapsomere space. 

P 4 SID protein, 290-292 P 10 promoter, 9 P22 scaffolding protein chemistry of, 280-281 coat protein binding in, 277—279 domain strncmre of, 274 fnnctional domains of, 274—280 minor proteins, recruitment of, 276-277 oligomerization of, 275—276 procapsid exit in, 279—280 role of 272-274... 

Figure 4 Architecture of three-hybrid screens, (a) The classic, small-molecule-based, three-hybrid platform is shown. The three components of this systems are a DNA-binding protein fused to a known drug-binding domain (X), a bifunctional small molecule that binds X on one end and displays a query "bait" on the other, and a library of possible "prey" proteins (V) expressed as fusions to transcriptional activation domains. Assembly of the ternary complex recruits the activation domain to the promoter and initiates reporter gene expression. A partial list of examples is shown in the inset boxes because of space constraints, some relevant systems are absent, (b) The RNA-based, three-hybrid is assembled in a similar fashion except that the bifunctional ligand is an RNA molecule. The complex between the MS2 RNA and the MS2-coat protein is typically used as the anchoring interaction.

Specialized coat proteins, which are actually a multisubunit complex, called adaptins, trap specific membrane receptors (whichmove laterally through the membrane) in the coated pit by binding to a signal sequence (Tyr-X-Arg-Phe, where X = any amino acid) at the endocellular cafbo3 terminus of the receptor. This process ensures that the correct receptors are concentrated in the coated pit areas and minimizes the amount of extracellular fluid that is taken up in the cell. RME appears to require the GTP-binding protein dynamin, but the process by which dynamin is recruited to clathrin-coated pits remains unclear (21). 

COPI and COPII vesicles mediate anterograde or retrograde traffic between the endoplasmic reticulum and the Golgi apparatus (Lee et al, 2004). Generation of COP vesicles is a multi-event process that starts with the recruitment of small G-proteins and large coat complexes on the Golgi or the endoplasmic reticulum (ER) membrane. At the membrane surface, coat proteins collect transmembrane proteins and polymerize into a curved lattice. The lattice shapes the underlying membrane into a bud, which by membrane fission leads to the formation of an individual transport vesicle. After vesicle formation, the coat depolymerizes and the COP components are recycled in the cytosol for another round. 

The myristoylated Arf preparations described in this chapter have been used in a number of in vitro assays including GAP, GEF, and effector binding assays. The proteins are useful when efficient loading with GTP is needed. More critically, some Arf activities, such as recruitment of vesicle coat protein, are highly dependent on myristoylation. In these cases, use of a partially myristoylated Arf, particularly with preparation-to-preparation differences in the extent of myristoylation, can confound results and their clear interpretation. The methods described in this chapter require only one additional column beyond that required for purification of nonmyristoylated or partially myristoylated Arf and provide homogeneously myristoylated Arf preparations. 

Arfs have been shown to be responsible for membrane recruitment of coat protein complexes, including the COPI and AP-1 complexes (Nie et al, 2003 Shin and Nakayama, 2004). To examine whether interaction of Arf and the GAT domain is required for recruitment of GGAs onto TGN membranes, we performed the following experiments. When... 

COPII vesicles are transport intermediates from the endoplasmic reticulum. The process is driven by recruitment of the soluble proteins that form the coat structure called COPII from the cytoplasm to the membrane. 

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