Proteins in membranes

The molecular weights of all SERCA-type Ca " transport ATPases are in the range of 100-110 kDa. Their N-terminal sequences are similar Met-Glu-X(Ala, Asn, Glu, Asp)-X (Ala, Gly, He). The Met-Glu-X-X sequence serves as a signal for the acetylation of N-terminal methionine both in soluble and in membrane proteins [71,72]. 

Menziani, M.C., Fanelli, F., Cocchi, M. and De Benedetti, P.G. (1996) The heuristic-direct approach to quantitative structure-activity relationship analysis of ligand-G protein coupled receptor complexes, in Membrane Protein Models Experiment, Theory and Speculation (ed. J. Findlay), Bios Science Publications, pp. 113-131. 

Homologous proteins. Homologous proteins usually crystallize under very different conditions. For example, in our laboratory two homologous proteins crystallize in either 10 mM sodium acetate, pH 3.8, 5 mM DTT, and 50% (v/v) MPD (Weichsel et al, 1996), or 100 mM ammonium sulfate, 30% PEG 6000, and 10 mM DTT (Filson et al, 2003). This technique was first used by Kendrew for solving the structure of sperm whale myoglobin (Kendrew et al., 1954) and has been used in many other structural studies. Currently, this technique is heavily exploited in membrane protein crystallography (Wiener,... 

Much research has been invested to identify a common and validated test method that may be used in all industrial laboratories concerned by phototoxicology. Cultured mammalian cells constitute an essential model for the evaluation of phototoxicity. Such systems include all biological targets (lipids in membranes, proteins, nucleic acids) as well as active pathways likely to modulate the phototoxic impact (apoptotic pathways, cellular defenses, endogenous antioxidants, repair pathways, metabolism). 

The question as to what the dielectic constant is of a membrane is difficult to answer because a membrane is of molecular dimensions whereas a dielectric constant is well defined only for a macroscopic system. Perhaps the essential point to note is that electrostatic interactions clearly are of great importance in membrane-protein interactions. 

The shift to longer wavelengths of the ORD Cotton effects upon aggregation of lipid-free membrane protein must arise from a unique kind of association or an association which, if not qualitatively unique, is more dominant in membrane protein than in other proteins. Since the... 

Role of PI in membrane protein anchoring Specific proteins can be covalently attached via a carbohydrate bridge to membrane-bound PI (Figure 17.9). [Note Examples of such proteins include alkaline phosphatase (a digestive enzyme found on the surface of the small intestine that attacks organic phosphates), and acetylcholine esterase (an enzyme of the postsynaptic membrane that... 

Essen L., Siegert R, Lehmann WD, Oesterhelt D (1998) Lipid patches in membrane protein oligomers crystal structure of the bacteriorhodopsin-lipid complex. Proc. Natl. Acad. Sci. USA 95(20) 11673-11678... 

Reisdorf WC, Krimm S. Infrared Dichroism of amide I and amide II modes of a - and atn-hclix segments in membrane proteins. Biophys I 1995 69 271-273. 

Coughenour HD, Spaulding RS, Thompson CM. 2005. The synaptic vesicle proteome A comparative study in membrane protein identification. Proteomics 4 3141-3155. 

Williams, R.W. Experimental Determination of Membrane Protein Secondary Structure Using Vibrational and CD Spectroscopies. In Membrane Protein Structure, White, S., Ed. Oxford University New York, in press. 

One of the most conspicuous features of residue distributions in membrane proteins is an aromatic belt, which sandwiches the apolar transmembrane domain. When aromatic residues are specifically displayed in membrane protein structures, a clustering in the interfacial region is often quite obvious. One example is shown in Fig. 3 (see color insert). Umschneider and Samsom (2001) have noted that this irregular distribution is restricted to Trp, His, and Tyr side chains, with Phe showing little preference for its location in the membrane. Thus, it appears that aromaticity and amphilicity are the preferred features. This aromatic belt reflects the favorable partitioning of aromatic amino acids into the interfacial region (Wimley and White, 1996 Yau et al., 1998) and may act to stabilize the orientation of the entire membrane protein or individual helices in the bilayer. 

Curvature stress could play an important role not only in the lipid phase but also in membrane protein stability. A membrane protein might... 

---