J Biol Chem 2003 May 14
Bates IR, Boggs JM, Feix JB, Harauz G.
Molecular Biology Genetics, University of Guelph, Guelph, Ontario N1G 2W1.
Myelin basic protein (MBP) maintains the compaction of the myelin sheath in the central nervous system by anchoring the cytoplasmic face of the two apposing bilayers, and may also play a role in signal transduction.
Site-directed spin labeling was done at 8 matching sites in each of two recombinant murine MBPs, qC1 (charge +19) and qC8 charge (+13), which respectively emulate the native form of the protein (C1) and a post-translationally modified form (C8) that is increased in multiple sclerosis (MS).
When interacting with large unilamellar vesicles, most spin-labeled sites in qC8 were more mobile than those in qC1.
Depth measurement via continuous wave power saturation indicated that the N-terminal and C-terminal sites in qC1 were located below the plane of the phospholipid headgroups.
In qC8, the C-terminal domain dissociated from the membrane, suggesting a means by which the exposure of natural C8 to cytosolic enzymes and ligands might increase in vivo in MS.
The importance of two FF pairs in MBP to its interactions with lipids was investigated by separately mutating each pair to AA.
The mobility at F42A-F43A and especially F86A-F87A increased significantly.
Depth measurements and helical wheel analysis indicated that the F86-F87 region could form a surface-seeking amphipathic alpha-helix.