Conformation of brain proteolipid apoprotein |
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Authors: | P Carmona M de Cozar L M Garcia-Segura J Monreal |
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Institution: | (1) Instituto de Neurobiologia S. R. Cajal (C.S.I.C.), Velazquez 144, E-28006 Madrid, Spain;(2) Instituto de Optica (C.S.I.C.), Serrano 121, E-28006 Madrid, Spain |
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Abstract: | 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 -helical structure, as well as the presence of minor -strands and random coil forms. The effect of sonication and a non-denaturing detergent, (n-octyl--d-glucopyranoside), on the structure of the protein have also been investigated. Sonication produces an increase of the and unordered structures at the expense of the -helical conformation. These structural changes are enhanced in the presence of the non-ionic detergent n-octyl--d-glucopyranoside. Lipids protect the native protein structure from the effects of sonication. The aforementioned detergent changes the PLA conformation by increasing the -helical content at the expense of -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. |
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Keywords: | Proteolipid apoprotein structure sonication non-denaturing detergent freeze-fracture electron microscopy infrared spectra |
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