All-Atom Ensemble Modeling of Detergent Association to Membrane Proteins

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Small-angle scattering techniques are low-resolution techniques that can give information on the shape and size of complex systems in solution. When applied to membrane proteins, the contribution to the scattering signal of the detergent molecules present in the sample is significant and needs to be dealt with. This is the case for x-ray scattering but most of the times also for neutron scattering, since the amphiphilic nature of the detergent molecules results in residual scattering contributions even at the contrast variation match point (which, ideally, would mask the scattering contribution of the detergent).

The image on the cover of the July 1, 2014, issue of the Biophysical Journal shows a low-resolution surface representation of the bacterial outer membrane transporter FhaC, which is the first and prototypical structure of the Omp85 superfamily of protein transporters. The protein is surrounded by a belt of all-atom detergent molecules, covering the hydrophobic beta barrel of the protein. Here, only one configuration out of an ensemble of possible detergent arrangements is shown.

In this work, we show that explicit modeling of a protein-detergent complex, combined with small-angle neutron scattering and contrast variation can yield excellent results and provide valuable information on both the protein conformation as well as the organization of the detergent belt.

The flexibility and general applicability of the method make it an extremely powerful and significant tool for the study of membrane proteins, including their conformational span. For more information, do not hesitate to contact any of the authors.

This work was the result of a collaborative effort involving five research teams in France:

Center for Infection and Immunity of Lille:
Bacterial respiratory infections

Interdisciplinary Research Institute, Lille:
Computational molecular systems biology
Transcriptional regulation and mediator

Structural Biology Institute, Grenoble:
Membrane and pathogens

Structural Biology Institute and Institut Laue Langevin, Grenoble:
Extremophiles and large molecular assemblies

– Marc F. Lensink, Frank Gabel, Françoise Jacob-Dubuisson, Bernard Clantin, Vincent Villeret, Christine Ebel

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