NMR solution structure of human cannabinoid receptor-1 helix 7/8 peptide: Candidate electrostatic interactions and microdomain formation

• Published in: Biochemical and biophysical research communications 2009-12, Vol.390 (3), p.441-446
• Main Authors: Tyukhtenko, Sergiy, Tiburu, Elvis K., Deshmukh, Lalit, Vinogradova, Olga, Janero, David R., Makriyannis, Alexandros
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Cannabinergic ligand; G protein-coupled receptor; Humans; Interhelical microdomain; Molecular Sequence Data; Nuclear Magnetic Resonance, Biomolecular; Peptides - chemistry; Proline kink; Protein Structure, Secondary; Protein Structure, Tertiary; Receptor, Cannabinoid, CB1 - chemistry; Signal transduction; Static Electricity; Structural biology; Transmembrane protein
• ISSN: 0006-291X; 1090-2104
• DOI: 10.1016/j.bbrc.2009.09.053

We report the NMR solution structure of a synthetic 40-mer (T 377–E 416) that encompasses human cannabinoid receptor-1 (hCB1) transmembrane helix 7 (TMH7) and helix 8 (H8) [hCB1(TMH7/H8)] in 30% trifluoroethanol/H 2O. Structural features include, from the peptide’s amino terminus, a hydrophobic α-helix (TMH7); a loop-like, 11 residue segment featuring a pronounced Pro-kink within the conserved NPxxY motif; a short amphipathic α-helix (H8) orthogonal to TMH7 with cationic and hydrophobic amino-acid clusters; and an unstructured C-terminal end. The hCB1(TMH7/H8) NMR solution structure suggests multiple electrostatic amino-acid interactions, including an intrahelical H8 salt bridge and a hydrogen-bond network involving the peptide’s loop-like region. Potential cation–π and cation–phenolic OH interactions between Y 397 in the TMH7 NPxxY motif and R 405 in H8 are identified as candidate structural forces promoting interhelical microdomain formation. This microdomain may function as a flexible molecular hinge during ligand-induced hCB1 conformer transitions.