Grégory Vernier
Conformational diversity and versatility of proteins/lipids interactions. A case study of α-lactalbumin and apomyoglobin
Published on 6 January 2006
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Thesis presented January 06, 2006
Abstract:
Besides transmembrane proteins, some soluble proteins, the so-called amphitropic proteins, are driven to interact with membranes at one stage of their biological activity. Such proteins are excellent models to provide insight into the interactions between proteins and membranes. α
-lactalbumin and apomyoglobin was chosen as model of amphotropic proteins. The effect of the proton and cofactor together with those of the physicochemical properties of the lipid bilayer, such as the curvature and the charge of the membrane, are investigated. We performed centrifugation and fluorescence measurements to follow the binding of proteins to membranes. We also present H/D exchange experiments performed to characterize the state of the proteins when bound to vesicles and their sites of interaction with the membranes.
Our results show that the conformational state of α
-lactalbumin depends of membrane curvature. The regions anchoring the protein to the membrane are restricted to amphiphilic helices. H/D exchange experiments monitored by NMR also yield residue-level data that constitute comprehensive information providing a new point of view on the thermodynamics of the interactions between the protein and the membrane. In the case of apomyoglobin, our results suggest some inherent properties of the globin fold propitious to the interactions with lipid bilayers. In addition, the binding of apomyoglobin to membranes does not seem necessary for its biological activity. A molecular description of the membrane-binding states has been undertaken using H/D exchange experiments monitored by mass spectrometry.
Keywords:
α-lactalbumin, apomyoglobin, amphitropic proteins, liposomes, proteins-lipids interactions, H/D exchange
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