Structural similarity of a membrane protein in micelles and membranes
ABSTRACT The anisotropic spin interactions measured for membrane proteins in weakly oriented micelles and in oriented lipid bilayers provide independent and potentially complementary high-resolution restraints for structure determination. Here we show that the membrane protein CHIF adopts a similar structure in lipid micelles and bilayers, allowing the restraints from micelle and bilayer samples to be combined in a complementary fashion to enhance the structural information. Back-calculation and assignment of the NMR spectrum of CHIF in oriented lipid bilayers, from the structure determined in micelles, provides additional restraints for structure determination as well as the global orientation of the protein in the membrane. The combined use of solution and solid-state NMR restraints also affords cross-validation for the structural analysis.
Full-textDOI: · Available from: Peter Teriete, Aug 16, 2015
- SourceAvailable from: David Tulumello
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- "e l s e v i e r . c o m / l o c a t e / b b a m e m experiments have shown that native protein quaternary structure may be maintained in detergent environments  ; aspects of secondary and tertiary structure may be similar in lipid bilayer versus micelle environments ; and the overall fold of a protein may persist in detergents . We have recently observed that the interaction of designed TM segments with detergents is highly sequencedependent , and in many cases mimics the predicted in vivo formation of both helix–helix and protein–lipid interactions  . "
ABSTRACT: High-resolution structural analysis of membrane proteins by X-ray crystallography or solution NMR spectroscopy often requires their solubilization in the membrane-mimetic environments of detergents. Yet the choice of a detergent suitable for a given study remains largely empirical. In the present work, we considered the micelle-crystallized structures of lactose permease (LacY), the sodium/galactose symporter (vSGLT), the vitamin B(12) transporter (BtuCD), and the arginine/agmatine antiporter (AdiC). Representative transmembrane (TM) segments were selected from these proteins based on their relative contact(s) with water, lipid, and/or within the protein, and were synthesized as Lys-tagged peptides. Each peptide was studied by circular dichroism and fluorescence spectroscopy in water, and in the presence of the detergents sodium dodecylsulfate (SDS, anionic); n-dodecyl phosphatidylcholine (DPC, zwitterionic); n-dodecyl-β-d-maltoside (DDM, neutral); and n-octyl-β-d-glucoside (OG, neutral, varying acyl tail length). We found that (i) the secondary structures of the TM segments were statistically indistinguishable in the four detergents studied; and (ii) a strong correlation exists between the extent of helical structure of each individual TM segment in detergents with its helicity level as it exists in the full-length protein, indicating that helix adoption is fundamentally the same in both environments. The denaturing properties of so-called 'harsh' detergents may thus largely be due to their interactions with non-membranous regions of proteins. Given the consistency of structural features observed for each TM segment in a variety of micellar media, the overall results suggest that the structure likely corresponds to its relevant biological form in the intact protein in its native lipid bilayer environment.Biochimica et Biophysica Acta 01/2012; 1818(5):1351-8. DOI:10.1016/j.bbamem.2012.01.013 · 4.66 Impact Factor
Human Respiratory Syncytial Virus Infection, 11/2011; , ISBN: 978-953-307-718-5
- "The HSQC spectrum of 15 N labeled SH protein was tested in three detergents: DPC (medium-chain, zwitterionic), DHPC (short-chain, zwitterionic), and SDS (anionic) (Fig. 8). Although SDS is a harsh detergent, well-resolved spectra of membrane proteins have been recorded (Howell et al., 2005; Franzin et al., 2007; Teriete et al., 2007). In contrast, DPC and DHPC have a headgroup that closely mimics that of phosphatidylcholine, the most abundant headgroup in natural membranes, successfully used in KcsA (Yu et al., 2005), human phospholamban (Oxenoid & Chou, 2005), diacylglycerol kinase (Van Horn et al., 2009), Rv1761c from Mycobacterium tuberculosis (Page et al., 2009), influenza A M2 (Schnell & Chou, 2008) or HIV Vpu (Park et al., 2003). "
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- "Recently, we determined the NMR structure of non-phosphorylated FXYD1 in detergent micelles . The N-terminal transmembrane domain forms three rigidly connected helices (h1, h2, h3) and shares both significant amino acid sequence homology  as well as structural similarity   with the other FXYD proteins (Fig. 1). It is loosely connected to a 10-residue C-terminal cytoplasmic helix (h4) with a sequence unique to FXYD1, which contains the phosphorylation domain. "
ABSTRACT: FXYD1 (phospholemman) is a member of an evolutionarily conserved family of membrane proteins that regulate the function of the Na,K-ATPase enzyme complex in specific tissues and specific physiological states. In heart and skeletal muscle sarcolemma, FXYD1 is also the principal substrate of hormone-regulated phosphorylation by c-AMP dependent protein kinase A and by protein kinase C, which phosphorylate the protein at conserved Ser residues in its cytoplasmic domain, altering its Na,K-ATPase regulatory activity. FXYD1 adopts an L-shaped α-helical structure with the transmembrane helix loosely connected to a cytoplasmic amphipathic helix that rests on the membrane surface. In this paper we describe NMR experiments showing that neither PKA phosphorylation at Ser68 nor the physiologically relevant phosphorylation mimicking mutation Ser68Asp induces major changes in the protein conformation. The results, viewed in light of a model of FXYD1 associated with the Na,K-ATPase α and β subunits, indicate that the effects of phosphorylation on the Na,K-ATPase regulatory activity of FXYD1 could be due primarily to changes in electrostatic potential near the membrane surface and near the Na+/K+ ion binding site of the Na,K-ATPase α subunit.Biochimica et Biophysica Acta 11/2009; 1788(11-1788):2462-2470. DOI:10.1016/j.bbamem.2009.09.001 · 4.66 Impact Factor