Myelin peptides

Antibodies typically are able to recognize peptide sequences as small as 5-6 amino acids in length. For instance, IgE auto-antibodies were found to have clinical significance in multiple sclerosis by binding specifically to short 5- and 6-amino acid epitopes on the surface of myelin proteins (Mikol et al., 2006). 

Mikol, D.D., Ditlow, C., Usatin, D., Biswas, P., Kalbfleisch, J., Milner, A., and Calenoff, E. (2006) Serum IgE reactive against small myelin protein-derived peptides is increased in multiple sclerosis patients. 

Some aspects of multiple sclerosis are reflected in the animal model experimental autoimmune encephalomyelitis, which is induced by immunization of susceptible animals with appropriate encephalogenic proteins or peptides. In these animals, if cultured adult stem cell neurospheres are injected into the bloodstream, injected cells can find their way to damaged portions of the nervous system and improve function in mice. How the injected cells augmented the recovery process is unclear. One possibility is that cells recruited to the lesions differentiated into oligodendrocytes and generated new myelin sheaths, but this seems unlikely in the face of ongoing cellular destruction. 

Rostami, A., Gregorian, S. K., Brown, M. J. and Pleasure, D. E. Induction of severe experimental autoimmune neuritis with a synthetic peptide corresponding to the 53-78 amino acid sequence of the myelin P2 protein. J. Neuroimmunol. 30 145-151,1990. 

On the other hand, basic myelin protein and monomeric melittin are proteins which, by many criteria, are devoid of ordered structure in aqueous solutions. This results in freedom of rotation of tryptophan residues which are exposed to the solvent. Such a situation may exist for peptides without regular structure and for denatured proteins. 

McCue D, Ryan K, Wraith DC, Anderton SM Activation thresholds determine susceptibility to peptide-induced tolerance in a heterogeneous myelin-reactive T cells repertoire. J Neuroimmunol 2004 156 96-106. 

Myelin Oligodendrocyte Glycoprotein (MOG) Peptide Fragment Rat (Sigma-Aldrich, MO, USA). 

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. 

Grogan, J.L., Kramer, A., Nogai, A., et al. (1999) Cross-reactivity of myelin basic protein-specific T cells with multiple microbial peptides Experimental autoimmune encephalomyelitis induction in TCR transgenic mice. J. Immunol. 163, 3764-3770. 

Second, a myelin protein (the A-l protein) accepts 2-acetamido-2-deoxy-D-galactose from uridine 5 -(2-acetamido-2-deoxy-D-galacto-pyranosyl pyrophosphate) when treated with a 2-acetamido-2-deoxy-D-galactose transferase from bovine submaxillary gland, even though the protein normally occurs devoid of carbohydrate.132 The L-threonine residue number 98 is the site of attachment for the sugar, and the sequence at this region of the peptide is ... 

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