Membrane proteins, hydrophobic domain

It should be mentioned that in many cases direct comparisons of reported biological effects are very difficult. Due to amphiphilic properties, a significant part of the effect of resorcinolic lipids is related to their interaction with membranous structures and the hydrophobic domains of proteins and therefore, the molar ratios rather than absolute concentrations should be used as a actual measure. The importance of this fact is clearly observed, e.g., in the studies of hemolytic concentration dependence on the number of erythrocytes used in the tests and in the time dependence of this process [387]. 

These cytosolic proteins contain five EF-hand domains and are able to translocate to the plasma membrane upon calcium binding [5]. In addition to the EF-hand domains, these proteins also have a hydrophobic glycine/proline-rich domain, important for their translocation to the membrane. To date five members of this... 

Rieske proteins are constituents of the be complexes that are hydro-quinone-oxidizing multisubunit membrane proteins. All be complexes, that is, bci complexes in mitochondria and bacteria, b f complexes in chloroplasts, and corresponding complexes in menaquinone-oxidizing bacteria, contain three subunits cytochrome b (cytochrome 6e in b f complexes), cytochrome Ci (cytochrome f in b(,f complexes), and the Rieske iron sulfur protein. Cytochrome 6 is a membrane protein, whereas the Rieske protein, cytochrome Ci, and cytochrome f consist of water-soluble catalytic domains that are bound to cytochrome b through a membrane anchor. In Rieske proteins, the membrane anchor can be identified as an N-terminal hydrophobic sequence (13). 

The pecM gene encodes a protein of 297 amino acids with a calculated molecular mass of 32 kDa. The predicted PecM protein displays the characteristics of an integral membrane protein since it is largely hydrophobic, with potential trans-membrane domains. SubceUular firactionation confirmed that PecM is anchored into the bacterial inner membrane whereas PecS is... 

Integral membrane proteins with one transmembrane domain may have soluble domains at either or both surfaces. An example of a monotopic protein, cytochrome b5 has a single hydrophobic segment that forms a hairpin loop, acting as an anchor to the cytoplasmic surface but probably not totally penetrating the bilayer. 

Photosystem I is a membrane pigment-protein complex in green plants, algae as well as cyanobacteria, and undergoes redox reactions by using the electrons transferred from photosystem II (PS II) [1], These membrane proteins are considered to be especially interesting in the study of monomolecular assemblies, because their structure contains hydrophilic area that can interact with the subphase as well as hydrophobic domains that can interact either with each other or with detergent and lipids [2], Moreover, studies with such proteins directly at the air-water interface are expected to be a valuable approach for their two-dimensional crystallization. 

Fig. 5.1 Schematic drawing of membrane association modes of peptides A Integral membrane proteins (1) major fd coat protein gpVIII of bacteriophage Ml 3 (pdb lfdm), anchored by an 18-residue trans-membrane hydrophobic helix (2) bovine rhodopsin, a 7 trans-membrane domain (G-protein-coupled) receptor (pdb lf88) (3) ion channel peptaibol Chrysospermin C (pdb lee7), and B Peripheral membrane proteins (1) neuro-...

The inner envelope membrane proteins have a cleavable N-terminal transit peptide, as well as some hydrophobic domain (s) in their mature portion. There are two possibilities on the role of this hydrophobic domain it may work as an N-terminal signal peptide after the translocation into the stroma and the subsequent cleavage of the transit peptide. Alternatively, it may work as a stop-transfer signal. One more important question is how the distinction is made between the outer membrane proteins, the inner membrane proteins, and the thylakoid membrane proteins. It is still an enigma. 

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