Chemosensory protein from the moth Mamestra brassicae - Expression and secondary structure from H-1 and N-15 NMR

A group of ubiquitous small proteins (average 13 kDa) has been isolated fro m several sensory organs of a wide range of insect species. They are believ ed to be involved in chemical communication and perception (olfaction or ta ste) and have therefore been called chemo-sensory proteins (CSPs). Several CSPs have been identified in the antennae and proboscis of the moth Mamestr a brassicae. We have expressed one of the antennal proteins (CSPMbraA6) in large quantities as a soluble recombinant protein in Escherichia coli perip lasm. This 112-residue protein is a highly soluble monomer of 13 072 Da wit h a pI of 5.5. NMR data (H-1 and N-15) indicate that CSPMbraA6 is well fold ed and contains seven a helices (59 amino acids) and two short extended str uctures (12 amino acids) from positions 5 to 10 and from 107 to 112. Thirty -seven amino acids are involved in beta turns and coiled segments and four amino acids are not assigned in the NMR spectra (the N-terminus and the res idue 52 in the loop 48-53), probably due to their mobility. This is the fir st report on the expression and structural characterization of a recombinan t CSP.