Myelin Basic Protein, A Saucy Molecule With High Responsiveness to the Environment or Just an Unusual Membrane Protein? - Molecules: Nucleation, Aggregation and Crystallization - page 183

Table 1. Summary of Circular Dichroism (CD) Experiments Carried Out as shown
in Polverini et al., (1999) a

% β -sheet % Random % Other

% α -helix (antiparallel) % β -turn Coil Structures

LF-MBP dialyzed 10.0 9.0 15.4 56.8 8.8

versus 20 mM
Tris, pH = 8.0
LF-MBP in myelin 14.1 12.7 24.3 43.9 4.9

liposomes
LF-MBP in 20 mM

5.1 6.0 35.9 52.7 0.3

HEPES pH = 7.0
LF-MBP + CHAPS

8.6 7.2 32.4 51.7 0.1

LB-MBP dialyzed 28.1 9.6 29.4 23.3 7.5

versus 0.5%
CHAPS/20 mM
Tris + additives,
pH = 8.0
LB-MBP in myelin 17.6 22.6 27.7 29.7 2.3

liposomes
LB-MBP + CHAPS

23.8 20.3 27.9 28.0 0.0

a The minimum lipid content of the non-raft LB-MBP after dialysis was 1.5 mg phospholipids/mg
protein. The relative amounts of secondary structure in the proteins were evaluated with the convex
constraint analysis (CCA) method, developed by Perczel et al . (1991, 1992).

Concluding Remarks

Knowledge of the structure of myelin proteins and in particular of MBP is
very important to understand the complex myelin structure, but also to
understand myelin degradation in MS and to devise effective strategies for
therapeutic management. However, we do not know the native three-
dimensional MBP conformation since the protein has never been crystal-
lized. This failure can be ascribed to the fact that the starting material was
not homogeneous but rather a mixture of MBPs (classic, acid-extracted
and water-soluble MBPs), never being able to re-attain their inherent
structure, even when reconstituted with lipids.
It is now clear that MBP exists in the form of multiple isomers dis-
tributed in different microdomains of myelin. About 90-95% of the MBPs