The basic protein of myelin (called MBP) is an extrinsic protein of the mye
lin membrane. Its structure and function are still unknown. MBP has been ex
tensively studied in its water-soluble form, but it is also known in a dete
rgent-soluble form, which is purified with endogenous myelin lipids and sho
uld correspond to the native form of the protein in the membrane. In order
to acquire insight into the structure of MBP, we have carried out circular
dichroism (CD) experiments on the protein both in the lipid-free and in the
lipid-bound form. Our data clearly show that lipid-free MBP is mainly diso
rdered with only a small amount having alpha-helix and beta-sheet motifs. O
n the other hand, the lipid-bound form of MBP appears to have a consistent
amount of ordered secondary structure. Theoretical predictions, made using
different computational methods, substantially confirm the tendency of the
protein to assume an ordered secondary structure in accordance with our CD
results.