Vesicles formation

A pre-requisite for clathrin-coat assembly is the recruitment to the membrane of an adaptor complex. Similar to what has been observed for the recruitment of coatomer to Golgi membranes, adaptor binding is dependent on the presence of ARF-GTP. However, in contrast to COPI vesicle formation, ARF-GTP is suggested to act in a process before budding and not as a stoichiometric coat component. Other differences between COP-coated and clathrin-coated vesicles concern their uncoating mechanism. Disassembly of clathrin-coated vesicles is believed to depend on the chaperoneHSC 70 and on auxilin. 

Membrane Proteins in Vesicle Formation and Cargo Selection... 

Huang, C. H. (1969). Studies on phosphatidylcholine vesicles. Formation and physical characteristics, Biochemistry. 8, 344-352. 

Ueno, M., Tanford, C., and Reynolds, J. A. (1984). Phospholipid vesicle formation using nonionic detergents with low monomer solubility. Kinetic factors determine vesicle size and polydis-persity. Biochemistry, 3070-3076. 

Other small monomeric GTPases (eg, ARF, Rab, Ras, and Rho) are important in various cellular processes such as vesicle formation and transport (ARF and Rab see below), cettain growth and differentiation processes (Ras), and formation of the actin cytoskele-ton. A process involving GTP and GDP is also crucial in the ttanspott of ptoteins across the membrane of the ER (see below). 

Vesicles lie at the heart of intracellular transport of many proteins. Recently, significant progress has been made in understanding the events involved in vesicle formation and transport. This has transpired because of the use of a number of approaches. These include establishment of cell-free systems with which to study vesicle formation. For instance, it is possible to observe, by electron microscopy, budding of vesicles from Golgi preparations incubated with cytosol and ATP. The development of genetic approaches for studying vesicles in yeast has also been crucial. The piemre is complex, with its own nomenclamre (Table 46-7), and involves a variety of cytosolic and membrane proteins, GTP, ATP, and accessory factors. 

Huang, C. Studies of Phosphatidylcholine Vesicles. Formation and Physical Characteristics, Biochemistry, 1969, 8, 344. 

Fig. 21.4. Vesicle formation and patch-clamp techniques used to record levamisole receptor channel currents from Ascaris muscle. (A) Muscle membrane vesicles bud-off from the bag membrane following a 10 min collagenase treatment and incubation for 1 h at 37°C in Ascaris saline. (B) Levamisole is applied to the outside surface of the membrane to activate receptor channels cell-attached patches are usually used but it is also possible to make inside-out and outside-out patch recordings.

The great importance of minerals in prebiotic chemical reactions is undisputed. Interactions between mineral surfaces and organic molecules, and their influence on self-organisation processes, have been the subject of much study. New results from Szostak and co-workers show that the formation of vesicles is not limited to one type of mineral, but can involve various types of surfaces. Different minerals were studied in order to find out how particle size, particle shape, composition and charge can influence vesicle formation. Thus, for example, montmorillonite (Na and K10), kaolinite, talc, aluminium silicates, quartz, perlite, pyrite, hydrotalcite and Teflon particles were studied. Vesicle formation was catalysed best by aluminium solicate, followed by hydrotalcite, kaolinite and talcum (Hanczyc et al., 2007). 

Trapped air and expansion of heated air in the soil are the cause of vesicle formation. When the air is driven out by infiltrating rain or floodwater, and cannot escape downwards, it escapes through the upper surface of the soil. When the soil surface is neither covered by stone, nor sealed by crusts, the vesicles are of a temporary nature only. When,... 

Regardless of their method of fabrication, most liposome preparations need to be further classified and purified before use. To remove excess aqueous components that were not encapsulated during the vesicle formation process, gel filtration using a column of Sephadex G-50 or dialysis can be employed. To fractionate the liposome population according to size, gel filtration using a column of Sepharose 2B or 4B should be done. 

Biotinylated liposomes usually are created by modification of PE components with an amine-reactive biotin derivative, for example NHS-LC-Biotin (Chapter 11, Section 1). The NHS ester reacts with the primary amine of PE residues, forming an amide bond linkage (Figure 22.19). A better choice of biotinylation agent may be to use the NHS-PEG -biotin compounds (Chapter 18), because the hydrophilic PEG spacer provides better accessibility in the aqueous environment than a hydrophobic biotin spacer. Since the modification occurs at the hydrophilic end of the phospholipid molecule, after vesicle formation the biotin component protrudes out from the liposomal surface. In this configuration, the surface-immobilized biotins are able to bind (strept)avidin molecules present in the outer aqueous medium. 

Schmid, S. L. Clathrin-coated vesicle formation and protein sorting an integrated process. Annu. Rev. Biochem. 66 511-548,1997. 

Fig. 13 Phase diagram of PS310-PAA52 in dioxane/water mixtures (A). Shaded regions between sphere and rod phases and between rod and vesicle phases correspond to coexistence regions. Reversibility of vesicle formation and growth process for PS300-PAA44 as function of THF/dioxane composition of nonselective solvent (B). Reprinted with permission from [239]. Copyright (2002) American Association for the Advancement of Science...

Kirchhausen, T., Bonifacino, J., and Riezman, H. (1997). Linking cargo to vesicle formation receptor tail interactions with coat proteins. Curr. Opin. Cell Biol. 9, 488-495. 

Mimms LT, Zampighi G, Nozaki Y, Tanford C, Reynolds JA. Phospholipid vesicle formation and transmembrane protein incorporation using octyl gluco-side. Biochemistry 1981 20 833. 

Another concern with freeze-drying LEH is the instability of liposome structure upon lyophilization. Vesicle formation occurs in the presence of bulk water and when water is removed, loss of structural integrity is inevitable. Fusion, crystal formation, and phase transition are observed, resulting... 

Minshall RD, Timppathi C, Vogel SM, et al. Endothelial cell-surface gp60 activates vesicle formation and trafficking via G(i)-coupled Src kinase signaling pathway. J Cell Biol 2000 150(5) 1057-1070. 

The recombinant inhibitors block different steps in coated pit/vesicle formation... 

For the formation of clathrin-coated vesicles, several proteins are required. Currently, there are several recombinant inhibitors available, which block different steps of coated pit/vesicle formation for example, amphiphysin (53), clathrin assembly protein AP180 (54), epsin (55), and clathrin mutant (56). 

Dynamin is a small motor protein with GTPase activity, which is involved in vesicle formation and the pinch-off of coated vesicles from the plasma membrane. Although it was originally thought that dynamin was specific to clathrin-mediated uptake, it has become clear that dynamin functions... 

Clague Ml, Urbe S, Aniento F, Gruenberg J. Vacuolar ATPase activity is required for endosomal carrier vesicle formation. J Biol Chem 1994 269(1) 21-24. 

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