title: Membrane protein structural validation by oriented sample solid-state NMR: diacylglycerol kinase.
abstract: The validation of protein structures through functional assays has been the norm for many years. Functional assays perform this validation for water-soluble proteins very well, but they need to be performed in the same environment as that used for the structural analysis. This is difficult for membrane proteins that are often structurally characterized in detergent environments, although functional assays for these proteins are most frequently performed in lipid bilayers. Because the structure of membrane proteins is known to be sensitive to the membrane mimetic environment, such functional assays are appropriate for validating the protein construct, but not the membrane protein structure. Here, we compare oriented sample solid-state NMR spectral data of diacylglycerol kinase previously published with predictions of such data from recent structures of this protein. A solution NMR structure of diacylglycerol kinase has been obtained in detergent micelles and three crystal structures have been obtained in a monoolein cubic phase. All of the structures are trimeric with each monomer having three transmembrane and one amphipathic helices. However, the solution NMR structure shows typical perturbations induced by a micelle environment that is reflected in the predicted solid-state NMR resonances from the structural coordinates. The crystal structures show few such perturbations, especially for the wild-type structure and especially for the monomers that do not have significant crystal contacts. For these monomers the predicted and observed data are nearly identical. The thermostabilized constructs do show more perturbations, especially the A41C mutation that introduces a hydrophilic residue into what would be the middle of the lipid bilayer inducing additional hydrogen bonding between trimers. These results demonstrate a general technique for validating membrane protein structures with minimal data obtained from membrane proteins in liquid crystalline lipid bilayers by oriented sample solid-state NMR.
authors.affiliation: National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida; Institute of Molecular Biophysics, Florida State University, Tallahassee, Florida.
authors.forename: Dylan T
authors.initials: DT
authors.lastname: Murray
authors.affiliation: State Key Laboratory of Magnetic Resonance and Molecular and Atomic Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan, PR China.
authors.forename: Conggang
authors.initials: C
authors.lastname: Li
authors.affiliation: Del Shankel Structural Biology Center, University of Kansas, Lawrence, Kansas.
authors.forename: F Philip
authors.initials: FP
authors.lastname: Gao
authors.affiliation: National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida; Department of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida.
authors.forename: Huajun
authors.initials: H
authors.lastname: Qin
authors.affiliation: National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida; Institute of Molecular Biophysics, Florida State University, Tallahassee, Florida; Department of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida. Electronic address: cross@magnet.fsu.edu.
authors.forename: Timothy A
authors.initials: TA
authors.lastname: Cross
mesh_terms: D019852:Diacylglycerol Kinase / Q000737:chemistry*; D057927:Hydrophobic and Hydrophilic Interactions; D009682:Magnetic Resonance Spectroscopy; D008565:Membrane Proteins / Q000737:chemistry*; D008958:Models, Molecular; D017433:Protein Structure, Secondary; D015203:Reproducibility of Results
chemical_list: D008565:Membrane Proteins; D019852:Diacylglycerol Kinase
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