Myelin Membrane Structure and Composition Correlated: A Phylogenetic Study

Abstract

We have correlated myelin membrane structure with biochemical composition in the CNS and PNS of a phylogenetic series of animals, including elasmobranchs, teleosts, amphibians, and mammals. X-ray diffraction patterns were recorded from freshly dissected, unfixed tissue and used to determine the thicknesses of the liquid bilayer and the widths of the spaces between membranes at their cytoplasmic and extracellular appositions. The lipid and protein compositions of myelinated tissue from selected animals were determined by TLC and sodium dodecyl sulfate-polyacrylamide gel electrophoresis/immunoblotting, respectively. We found that (1) there were considerable differences in lipid (particularly glycolipid) composition, but no apparent phylogenetic trends; (2) the lipid composition did not seem to affect either the bilayer thickness, which was relatively constant, or the membrane separation; (3) the CNS of elasmobranch and teleost and the PNS of all four classes contained polypeptides that were recognized by antibodies against myelin P0 glycoprotein; (4) antibodies against proteolipid protein (PLP) were recognized only by amphibian and mammalian CNS; (5) wide extracellular spaces (ranging from 36 to 48 A) always correlated with the presence of P0-immunoreactive protein; (6) the narrowest extracellular spaces (approximately 31 A) were observed only in PLP-containing myelin; (7) the cytoplasmic space in PLP-containing myelin (approximately 31 A) averaged approximately 5 A less than that in P0-containing myelin; (8) even narrower cytoplasmic spaces (approximately 24 A) were measured when both P0 and 11-13-kilodalton basic protein were detected; (9) proteins immunoreactive to antibodies against myelin P2 basic protein were present in elasmobranch and teleost CNS and/or PNS, and in mammalian PNS, but not in amphibian tissues; and (10) among mammalian PNS myelins, the major difference in structure was a variation in membrane separation at the cytoplasmic apposition. These findings demonstrate which features of myelin structure have remained constant and which have become specifically altered as myelin composition changed during evolutionary development.

P0 (Protein Zero) Mutation S34C Underlies Instability of Internodal Myelin in S63C Mice

“…6B), which is close to that observed for S63C(Ϫ/Ϫ) (Table 3), compared with the ϳ47 Å spacing found in the WT (Fig. 6A) (2,36).…”

Peripheral myelin of Xenopus laevis: Role of electrostatic and hydrophobic interactions in membrane compaction

“…~180 Å for mammals, ~177 Å for rodents, ~171 Å for frog, and ~161 Å for fish (Schmitt et al, 1935;Fernandez-Moran and Finean, 1957;Hoglund and Ringertz, 1961;Finean and Burge, 1963;Moody, 1963;Blaurock, 1967;Akers and Parsons, 1970;Caspar and Kirschner, 1971;Chandross et al, 1978;Blaurock et al, 1986;Kirschner et al, 1989;Mateu et al, 1990). These differences derive mostly from differences in the widths of the extracellular and cytoplasmic appositions between membrane bilayers, and correlate generally with the sizes of the respective domains of P0 or P0-like proteins Inouye and Kirschner, 1990;Inouye and Kirschner, 1991;Avila et al, 2007).…”

Three-dimensional Structure of Myelin Basic Protein

“…Residues around this triproline segment are often modified. Myelin basic protein has a number of sequence and other similarities with other protein families (18,19). Properties such as charge density, post-translational modification by addition of fatty acids, and overall hydrophobicity are similar in MBP and proteolipid protein from the central nervous system and in the pulmonary surfactant proteins SP-B and SP-C (20).…”