Membrane proteins insertion

Most of the data available on membrane protein insertion has been generated for members of the mitochondrial carrier family (MCF), particularly for AAC, the model precursor. 

Fig. 1. Model for membrane protein insertion into the ER membrane. In stage I, an N-terminal signal peptide (not shown) has already initiated translocation across the membrane.

Chloroplasts in higher plants have three membranes the outer and inner envelope membranes and the thylakoid membrane. Very little is known about membrane protein assembly into the two envelope membranes (Soil and Tien, 1998). The thylakoid has been better studied and in fact appears to use mechanisms very similar to those found in E. coli for membrane protein insertion (Dalbey and Robinson, 1999). Thus, SRP, SecA, SecYEG, YidC, and Tat homologues are all present in the thylakoid membrane or in the stroma (the Tat system was first identified in thylakoids, in fact). In contrast to E. coli, however, there are thylakoid proteins that appear to insert spontaneously into the membrane, insofar as no requirement for any of the known translocation machineries has been detected (Mant et al, 2001). 

White SH. Membrane protein insertion the biology-physics nexus. 

The study of protein function is increasingly focused on the interactions between protein structure, electrochemical potentials, and molecular motion. For membrane proteins, insertion through a phospholipid bilayer imparts a defined orientation to the protein and a specified relation between the macroscopic electrical field and the axis of the molecule normal to the membrane. These constraints can be exploited to obtain detailed information about membrane protein function and dynamics, particularly for proteins that form aqueous pores through membranes. The ability to record currents that... 

Lorigan, G.A., Dave, P.C., Tiburu, E.K. et al. 2004. Sohd-state NMR spectroscopic studies of an integral membrane protein inserted into aligned phosphohpid bUayer nanotube arrays. J. Am. Chem. Soc. 126 9504-9505. 

Another bio-inspired approach is to design polymersomes as enclosed reaction compartments for the development of nanoreactors, nanodevices, or artificial organelles, in which active compounds are not only protected from the environment, but also allowed to act in situ. For such function, membrane permeability is of crucial importance, since it allows the exchange of substrates/products with the environment of the pol)maersomes. Various methods have been reported to generate polymersomes with permeable membranes (i) polymers forming intrinsically porous membranes, (ii) polymer membranes that are permeable to ions as e.g. specific oxygen species, (iii) pore formation in pH responsive polymer membranes by chemical treatment, (iv) polymer membrane permeabilization by UV-irradiation, and (v) biopores or membrane proteins inserted into polymer membranes. ... 

A) Schematic representation of membrane protein insertion into a solid-supported pol3rmer membrane using Bio-Beads. 

Solid-state NMR spectroscopic studies of an integral membrane protein inserted into aligned phospholipid bilayer nanotube arrays have been reported. 

Harley, C.A., Holt, J.A., Turner, R. Tipper, D.J. (1998) J. Biol. Chem., 249, 24963-24971. Trans-membrane protein insertion orientation in yeast depends on the charge difference across transmembrane segments, their total hydrophobicity, and its distribution. 

Figure 8. Image of labeled membrane proteins inserted into an artificial planar...

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