Conformation of brain proteolipid apoprotein. Effects of sonication and n-octyl-beta-D-glucopyranoside detergent.
The conformation of brain proteolipid apoprotein (PLA) has been investigated using infrared spectroscopy and freeze-fracture electron microscopy. For this purpose, spectroscopic samples consisting of a mixture of liquid paraffin and wet protein have been prepared. These systems have allowed us to record the infrared spectra of PLA at neutral pH. The amide I and III regions reveal the existence of a predominantly alpha-helical structure, as well as the presence of minor beta-strands and random coil forms. The effect of sonication and a non-denaturing detergent, (n-octyl-beta-D-glucopyranoside), on the structure of the protein have also been investigated. Sonication produces an increase of the beta and unordered structures at the expense of the alpha-helical conformation. These structural changes are enhanced in the presence of the non-ionic detergent n-octyl-beta-D-glucopyranoside. Lipids protect the native protein structure from the effects of sonication. The aforementioned detergent changes the PLA conformation by increasing the alpha-helical content at the expense of beta-sheet and random coil forms. Therefore the PLA structure seems to be similar to the structures of other proteins intrinsic to non-neural membranes. The effects investigated also suggest that PLA behaves in a conformationally flexible manner.
Carmona
P
P
Instituto de Neurobiologia S.R. Cajal (C.S.I.C.), Madrid, Spain.
de Cozar
M
M
Garcia-Segura
L M
LM
Monreal
J
J
D000577:Amides; D000818:Animals; D001059:Apoproteins / Q000648:ultrastructure*; D001923:Brain Chemistry; D002417:Cattle; D005614:Freeze Fracturing; D005960:Glucosides / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D009185:Myelin Proteins / Q000648:ultrastructure*; D018991:Myelin Proteolipid Protein; D011487:Protein Conformation / Q000187:drug effects; D013010:Sonication; D013055:Spectrophotometry, Infrared
D000577:Amides; D001059:Apoproteins; D005960:Glucosides; D009185:Myelin Proteins; D018991:Myelin Proteolipid Protein; C018619:octyl-beta-D-glucoside