Molecular organization of the human serotonin transporter at the air/waterinterface

The serotonin transporter (SERT) is the target of several important antidep ressant and psychostimulant drugs. It has been shown that under defined con ditions, the transporter spread at the air/water interface was able to bind its specific ligands, In this paper, the interfacial organization of the p rotein has-been assessed from dynamic surface pressure and ellipsometric me asurements. For areas comprising between 10 400 and 7100 Angstrom (2)/molec ule, ellipsometric measurements reveal an important change in the thickness of the SERT film. This change was attributed to the reorientation of the t ransporter molecules from a horizontal to their natural predictive transmem brane orientation. The thickness of the SERT film at 7100 Angstrom (2)/mole cule was found to be approximately equal to 84 Angstrom and coincided well with the theoretical value estimated from the calculations based on the dim ensions of alpha -helices containing membrane proteins. These data suggest that the three-dimensional arrangement of the SERT may be represented as a box with lengths d(z) = 83-85 Angstrom and d(y) or d(x) = 41-47 Angstrom. ( C) 2001 Federation of European Biochemical Societies. Published by Elsevier Science B.V. All rights reserved.