Biophysical Journal 55: 949-955 (1989)
© 1989 the Biophysical Society

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Binks, B P Articles by Waks, M Search for Related Content PubMed PubMed Citation Articles by Binks, B P Articles by Waks, M

Structural parameters of the myelin transmembrane proteolipid in reverse micelles.

Laboratoire de Spectroscopie Hertzienne, Paris, France.

ABSTRACT

The Folch-Pi proteolipid is the most abundant structural protein from the central nervous system myelin. This protein-lipid complex, normally insoluble in water, requires only a small amount of water for solubilization in reverse micelles of sodium bis (2-ethylhexyl) sulfosuccinate (AOT) in isooctane. The characterization of the proteolipid-free and proteolipid-containing micelles was undertaken by light scattering and fluorescence recovery after fringe pattern photobleaching (FRAPP) experiments. Quasi elastic light scattering (QELS) was carried out at a high (200 mM) AOT concentration, at low water-to-surfactant mole ratio (Wo = 7) and at increasing protein occupancy. Two apparent hydrodynamic radii, differing tenfold in size, were obtained from correlation functions. The smaller one (RaH = 5.2 nm) remains constant and corresponds to that measured for protein-free micelles. The larger one increases linearly with protein concentration. In contrast, FRAPP measurements of self-diffusion coefficients were found unaffected by the proteolipid concentration. Accordingly, they have been performed at constant protein/surfactant mole ratios. The equivalent RH, extrapolated to zero AOT concentration for protein-free reverse micelles (2.9 nm) and in the presence of the proteolipid (4.6 nm), do not reveal the mode of organization previously suggested by QELS measurements. The complex picture emerging from this work represents a first step in the characterization of an integral membrane protein in reverse micelles.