Myelin Amino acid sequence

There is a second family of small lipid-binding proteins, the P2 family, which include among others cellular retinol- and fatty acid-binding proteins as well as a protein, P2, from myelin in the peripheral nervous system. However, members of this second family have ten antiparallel p strands in their barrels compared with the eight strands found in the barrels of the RBP superfamily. Members of the P2 family show no amino acid sequence homology to members of the RBP superfamily. Nevertheless, their three-dimensional structures have similar architecture and topology, being up-and-down P barrels. 

The MBPs are extrinsic proteins localized exclusively at the cytoplasmic surface in the major dense line (Fig. 4-11), a conclusion based on their amino acid sequence, inaccessibility to surface probes and direct localization at the electron microscope level by immunocytochemistry. There is evidence to suggest that MBP forms dimers, and it is believed to be the principal protein stabilizing the major dense line of CNS myelin, possibly by interacting with negatively charged lipids. A severe hypomyelination and failure of compaction of the major dense line in MBP deficient shiverer mutants supports this hypothesis (Table 4-2). 

Members of this family of molecules may have only one Ig-like domain, as is the case for the myelin protein P0, or, as for most of the family, have many Ig domains. In addition to the subclassification of Ig domains into V-, C- and C2-like domains, Ig family members can be broadly divided into three general classes [8] (a) those that have only Ig-like domains (b) those that have Ig domains and additional domains that resemble regions of the ECM component fibronectin, termed FN-like domains and (c) those that have Ig domains and motifs other than FN-like domains. Moreover, any one Ig family member may have many isoforms, which may differ in the length of the cytoplasmic domain, in their post-translational modifications and whether they are membrane-spanning or glycosylphos-phatidylinositol (GPI)-anchored proteins (see Box 3-1). Also, additional amino acid sequences inserted in the extracellular domain may distinguish isoforms of a particular IgCAM. While it is not known how the majority... 

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. 

Because ALBP is related to several proteins of known structure, molecular replacement is an attractive option for phasing. The choice of a phasing model is simple here just pick the one with the amino-acid sequence most similar to ALBP, which is myelin P2 protein. Solution of rotation and translation functions refers to the search for orientation and position of the phasing model (P2) in the unit cell of ALBP. The subsequent paper provides more details. 

The initial model of ALBP was built by simply putting the amino acid sequence of ALBP into the molecular structure of myelin P2 protein. After a 20-step rigid-body refinement of the positions and orientations of the molecule, crystallographic refinement... 

Shaw, S. Y., Lawson, R. A., and Lees, M. B., Analagous amino acid sequence in myelin proteolipid and viral proteins, FEBS Lett., 207, 266, 1986. 

Salzer JL, Holmes WP, Golman DR. The amino acid sequences of the myelin-associated glycoproteins Homology to the immunoglobulin gene superfamily. / Cell Biol. 1987 104 959-965. 

Little is known about the specific requirements of the enzyme. Guinea pig brain enzyme specifically methylates only Arg-107 of the 19 arginine residues in an encephalitogenic basic protein of human myelin (204). The same residue is also methylated in a similar protein from monkey, bovine, rabbit, guinea pig, rat, chicken, and turtle (209). The amino acid sequence around Arg-107 of the bovine basic protein is... 

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). 

MAG is one of a set of cell-surface glycoproteins expressed by myelin-forming cells which have been hypothesized to mediate the apposition of the myelin sheath to the axon. Two forms of MAG are known which, similarly to NCAM, differ in the intracytoplasmic domain as a result of alternative splicing. The carboxy-terminal 318 amino acids of MAG are identical to the partial sequence so far obtained of a protein that has been designated as rat neuronal cytoplasmic protein 3 [184], However, the latter was previously believed to be a neuropeptide precursor and to be expressed in specific groups of neurons rather than in glial cells. The reason for this discrepancy is unclear. 

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