Application of on-line capillary electrophoresis /tandem mass spectrometry to the study of myelin basic proteins.

Abstract

On-line capillary electrophoresis-tandem mass spectrometry (CE-MS/MS) of posttranslational modifications (PTMs) of Myelin Basic Protein (MBP) charge isomer tryptic digests has been utilized to investigate spiny dogfish and human MBPs. CE has permitted rapid separations of mixtures with high resolution. The quadrupole ion trap storage/reflectron time-of-flight mass spectrometer has proven to be an efficient detection device for the CE eluent of tryptic peptides from spiny dogfish and human MBPs. The comparison of PTM of MBP from spiny dogfish and humans provides information for understanding the evolutionary process from nonmammalian vertebrate (spiny dogfish) to mammalian vertebrate (human). The current results demonstrate the presence of PTM in both spiny dogfish and human MBP and the connection between these two MBPs. The PTM sites on normal and Multiple Sclerosis forms of human MBP charge isomers have been investigated using the CE-MS/MS system. Multiple Sclerosis patients showed more extensive methylation than healthy persons on the arginine at residue 107 in charge isomers c4 and c5. Phosphorylation appeared much more frequently and intensively in normal than Multiple Sclerosis charge isomers. At the present time it is thought that the phosphorylation of MBP plays an important role in maintaining the tight wrappings of the myelin structure, and dephosphorylation facilitates the destabilization of myelin and permits attack by the immune system, which results in Multiple Sclerosis. Also, excellent correlation was observed for electrophoretic mobilities of tryptic peptides of human MBP with q/M<super>0.56</super>, where q is the calculated net charge and M is the molecular weight. Posttranslationally modified peptides also followed this correlation.