Solid-state NMR ¹³C and ¹⁵N resonance assignments of a seven-transmembrane helical protein Anabaena Sensory Rhodopsin.

Anabaena Sensory Rhodopsin (ASR) is a unique microbial rhodopsin that displays photocromism, interacts with soluble transducer, and may be involved in gene regulation. Here we report nearly complete spectroscopic (13)C and (15)N assignments of ASR reconstituted in lipids, obtained using two- and three-dimensional magic angle spinning solid state NMR spectroscopy on alternately (13)C labeled samples. The obtained chemical shifts are used to characterize the protein backbone conformation. They suggest that lipid-reconstituted ASR has a fold generally similar to that seen in earlier X-ray studies, but with a number of important differences. SSNMR detects double conformations for a number of residues on the cytoplasmic side.