Abstract
Biophysical investigation of membrane proteins generally requires their extraction from native sources using detergents, a step that can lead, possibly irreversibly, to protein denaturation. The propensity of dodecylphosphocholine (DPC), a detergent widely utilized in NMR studies of membrane proteins, to distort their structure has been the subject of much controversy. It has been recently proposed that the binding specificity of the yeast mitochondrial ADP/ATP carrier (yAAC3) toward cardiolipins is preserved in DPC, thereby suggesting that DPC is a suitable environment in which to study membrane proteins. In this communication, we used all-atom molecular dynamics simulations to investigate the specific binding of cardiolipins to yAAC3. Our data demonstrate that the interaction interface observed in a native-like environment differs markedly from that inferred from an NMR investigation in DPC, implying that in this detergent, the protein structure is distorted. We further investigated yAAC3 solubilized in DPC and in the milder dodecylmaltoside with thermal-shift assays. The loss of thermal transition observed in DPC confirms that the protein is no longer properly folded in this environment.
Highlights
In the context of membrane-protein structure determination, dodecylphosphocholine (DPC) has been the subject of much criticism for being a very harsh detergent, prone to induce protein denaturation [1,2,3,4,5]
The uncoupling protein (UCP2), for which a backbone fold has been determined [8], and the ADP/ATP carrier (AAC), have been thoroughly investigated in thermostability-shift assay (TSA) experiments [4,15]. These experiments have shown that in a mild dodecylmaltoside (DDM) detergent environment, mitochondrial carriers extracted from native membranes show many of the expected features
Molecular dynamics (MD) simulations indicated without any ambiguity that the putative structure of UCP2 determined by solution-state NMR in DPC [8], when inserted into membranes, collapses, suggesting that it is not a physiological state, and is possibly distorted beyond recovery by the harsh detergent environment
Summary
In the context of membrane-protein structure determination, dodecylphosphocholine (DPC) has been the subject of much criticism for being a very harsh detergent, prone to induce protein denaturation [1,2,3,4,5]. These experiments have shown that in a mild dodecylmaltoside (DDM) detergent environment, mitochondrial carriers extracted from native membranes show many of the expected features.
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