Comparative NMR analysis of an 80-residue G protein-coupled receptor fragment in two membrane mimetic environments.

Fragments of integral membrane proteins have been used to study the physical chemical properties of regions of transporters and receptors. Ste2p(G31-T110) is an 80-residue polypeptide which contains a portion of the N-terminal domain, transmembrane domain 1 (TM1), intracellular loop 1, TM2 and part of extracellular loop 1 of the α-factor receptor (Ste2p) from Saccharomyces cerevisiae. The structure of this peptide was previously determined to form a helical hairpin in lyso-palmitoylphosphatidyl-glycerol micelles (LPPG) [1]. Herein, we perform a systematic comparison of the structure of this protein fragment in micelles and trifluoroethanol (TFE):water in order to understand whether spectra recorded in organic:aqueous medium can facilitate the structure determination in a micellar environment. Using uniformly labeled peptide and peptide selectively protonated on Ile, Val and Leu methyl groups in a perdeuterated background and a broad set of 3D NMR experiments we assigned 89% of the observable atoms. NOEs and chemical shift analysis were used to define the helical regions of the fragment. Together with constraints from paramagnetic spin labeling, NOEs were used to calculate a transiently folded helical hairpin structure for this peptide in TFE:water. Correlation of chemical shifts was insufficient to transfer assignments from TFE:water to LPPG spectra in the absence of further information.

1H, 13C and 15N assignment of the GNA1946 outer membrane lipoprotein from Neisseria meningitidis.

GNA1946 (Genome-derived Neisseria Antigen 1946) is a highly conserved exposed outer membrane lipoprotein from Neisseria meningitidis bacteria of 287 amino acid length (31 kDa). Although the structure of NMB1946 has been solved recently by X-Ray crystallography, understanding the behaviour of GNA1946 in aqueuos solution is highly relevant for the discovery of the antigenic determinants of the protein that will possibly lead to a more efficient vaccine development against virulent serogroup B strain of N. meningitidis. Here we report almost complete (1)H, (13)C and (15)N resonance assignments of GNA1946 (residues 10-287) in aqueous buffer solution.