Proteolipids

The conformation of bovine myelin basic protein (MBP) in AOT/isooctane/water reversed micellar systems was studied by Waks et al. 67). This MBP is an extrinsic water soluble protein which attains an extended conformation in aqueous solution 68 but is more density packed at the membrane surface. The solubilization of MBP in the AOT reversed micelles depends on the water/AOT-ratio w0 68). The maximum of solubilization was observed at a w0-value as low as 5.56. The same value was obtained for another major protein component of myelin, the Folch-Pi proteolipid 69). According to fluorescence emission spectra of MBP, accessibility of the single tryptophane residue seems to be decreased in AOT reversed micelles. From CD-spectra one can conclude that there is a higher conformational rigidity in reversed micelles and a more ordered aqueous environment. 

In the case of myelin proteolipid solubilized in water/tetraethylene glycol monodo-decyl ether/dodecane microemulsions, its a-helical structure is preserved [176,177],... 

PLP Proteolipid protein PLT Primed lymphocyte typing PMA Phorbol myristate acetate PMC Peritoneal mast cell PMN Polymorphonuclear neutrophil... 

DPDPB has been used to study the endocytosis of cadherin from intracellular junctions (Troyanovsky et al., 2006), the subunit arrangement in the flagellar rotor assembly (Lowder et al., 2005), and the disease-associated mutations in myelin proteolipid protein in the endoplasmic reticulum (ER) (Swanton et al., 2005). DPDPB can be used to conjugate reduced antibody molecules to p-D-galactosidase using essentially the same protocol as that described by O Sullivan et al. (1979). 

Swanton, E., Holland, A., High, S., and Woodman, P. (2005) Disease-associated mutations cause premature oligomerization of myelin proteolipid protein in the endoplasmic reticulum. PNAS 102, 4342-4347. 

Jimpy mouse, rumpshaker mouse, myelin-deficient (md) rat, shaking dog X-linked Proteolipid protein (PLP) Variable degrees of oligodendrocyte death and CNS myelin deficiency, decreased spacing at intraperiod line of compact CNS myelin see text 1,9,10,43,44... 

Greer, J. M. and Lees, M. B. Myelin proteolipid protein-the first 50 years. Int. J. Biochem. Cell. Biol. 34, 211-215,2002. 

Hudson, L. D. Proteolipid protein gene. In R. A. Lazzarini (ed.), Myelin biology and disorders. San Diego, CA Elsevier Academic Press, 2004,401-420. 

Stecca, B., Southwood, C. M., Gragerov, A. et al. The evolution of lipophilin genes from invertebrates to tetrapods DM-20 cannot replace proteolipid protein in CNS myelin. /. Neurosci. 20,4002-4010, 2000. 

Gudz, T. I., Schneider, T. E., Haas, T. A. et al. Myelin proteolipid protein forms a complex with integrins and may participate in integrin receptor signaling in oligodendrocytes. /. Neurosci. 22,7398-7407, 2002. 

Frank, M. MAL, a proteolipid in glycosphingolipid enriched domains functional implications in myelin and beyond. Prog. Neurobiol. 60, 531-544, 2000. 

There are also Na+ pump y-subunits, a family of=15 kDa proteolipids that can associate with sodium pump a-subunits. However they are not necessary for pump activity nor are they expressed in all cells. The y-subunits are classed as members of the FXYD gene family and several are expressed in brain [5]. The kidney expresses almost exclusively Na+,K+ pumps with arsubunits throughout the functionally diverse segments of the nephron, but different y-subunits are expressed in different segments. From this it is inferred that different y-subunits optimize the sodium pump for operation under the varying ionic environments [6]. 

Another, but less well defined, class of molecules, some of whose members mediate adhesion interaction, is the four-transmembrane domain family, which shares similar hydropathy plots and may have similar dispositions with respect to the phospholipid bilayer, for example the myelin proteolipid proteins, the connexins of gap junctions, the ryanodine receptor and others. 

In the CNS of mammals, two proteins are needed to accomplish the dual role of adhesion at both myelin bilayer surfaces that P0 effects in the PNS. The four-trans-membrane-domain proteolipid protein (PLP) is likely to be responsible for adhesion of the extracellular surfaces, while the very basic cytoplasmic myelin basic protein... 

Kalwy, S. A. and Smith, R. Mechanisms of myelin basic protein and proteolipid protein targeting in oligodendrocytes. Mol. Membr. Biol. 11 67-78,1994. 

Imbalances of brain amino acids may hinder the synthesis of brain lipids, leading to a diminution in the rate of myelin formation. Decreases of lipids, proteolipids and cerebrosides (Ch. 3) have been noted in several of these syndromes, e.g. maple syrup urine disease, when intra-myelinic edema is a prominent finding, particularly during the acute phase of metabolic decompensation [9]. Pathological changes in brain myelin are common, especially in infants who die early in life. The fundamental... 

PLP proteolipid protein SCHAD short chain 3-hydroxyacyl-CoA dehydrogenase... 

Alves, I. D. Cowell, S. M. Salamon, Z. Devanathan, S. Tollin, G. Hruby, V. J., Different structural states of the proteolipid membrane are produced by ligand binding to the human 8 opioid receptor as shown by plasmon waveguide resonance spectroscopy, Mol. Pharmacol. 2004, 65, 1248 1257... 

Salamon, Z. Macleod, H. A. Tollin, G., Coupled plasmon waveguide resonators A new spectroscopic tool for probing proteolipid film structure and properties, Biophys. J. 1997, 73, 2791 2797... 

Muller V, Aufurth S, Rahlfs S. 2001. The Na -cycle in Acetobacterium woodii identification and characterization of a Na -translocating FiFo-ATPase with a mixed oligomer of 8 and 16-kDa proteolipids. Biochim Biophys Acta 1505 108-20. 

Rahlfs S, Aufurth S, Muller V. 1999. The Na -FiFo-ATPase operon from Acetobac-terium woodiv. operon structure and presence of multiple copies of atpE, which encode proteolipids of 8- and 18-kDa. J Biol Chem 274 33999 004. 

The most hydrophobic integral membrane proteins can be extracted into organic solvents such as mixtures of chloroform and methanol. One such proteolipid protein, the 23.5-kDa lipophilin, accounts for over half the protein of myelin.57 182 The purified protein from rat brain contains 66% of nonpolar amino acids and six molecules of covalently bound palmitic acid and other fatty acids per peptide chain in thioester linkage to cysteine side chains. This protein evidently has four transmembrane helical segments with the six fatty acid chains incorporated into the membrane bilayer. It also has cytoplasmic and extracellular loops, one of which binds inositol hexakisphosphate (Ins P-6). (Fig. 11-9).183 The myelin proteolipid is an essential component of the myelin sheath and defects in this protein are associated with some demyelinating diseases57 which are discussed in Chapter 30. 

The F0 portion of bacterial ATP synthase, which is embedded in the membrane, consists of one 271-residue subunit a, an integral membrane protein probably with five transmembrane helices,231 232 two 156-residue b subunits, and - twelve 79-residue c subunits. The c subunit is a proteolipid, insoluble in water but soluble in some organic solvents. The structure of monomeric c in chloroform methanol H20 (4 4 1) solution has been determined by NMR spectroscopy. It is a hairpin consisting of two antiparallel a helices.233 Twelve of the c subunits are thought to assemble into a ring with both the N and C termini of the subunit chains in the periplasmic (or intermembrane) face of the membrane.234 235 The ratio of c to a subunits has been difficult to measure but has been estimated as 9-12. The fact that both genetically fused c2 dimers and c3 trimers form function F0 suggested that they assemble... 

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