Brain proteolipid

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]. 

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... 

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. 

Major myelin proteolipid proteins, PLP and DM-20. In 1951 Folch and Lees discovered that a substantial amount of proteins from brain white matter could be... 

Gaitonde, M. K. The turnover of proteolipids and phosphatidopeptides in the brain in Brain lipids and lipoproteins, and the leu codystrophies , p. 42. Ed. J. Folch Pi and H. Bauer. Amsterdam-London-New York Elsevier 1963. 

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