Recombinant chemosensory protein (CSP2) from the moth Mamestra brassicae: crystallization and preliminary crystallographic study

Chemosensory proteins (CSPs) are small proteins (13 kDa on average) present in several sensory organs from a wide range of insect species. They are be lieved to be involved in chemoperception (olfaction or taste) and to play a role in chemical transport from air or water to chemosensitive receptors. Here, the first crystals of a CSP originating from the moth Mamestra brassi cae (Mbra) proboscis and expressed as recombinant protein in Escherichia co li periplasm are reported. Crystals of MbraCSP2 were obtained by the hangin g-drop vapour-diffusion method under the following conditions: 1 mul of a 4 6 mg ml(-1) protein solution in 50 mM Tris pH 8.0 containing cetyl alcohol as ligand (1:5 molar ratio) was mixed with 1 mul of well solution containin g 30% PEG 4000, 0.2 M sodium acetate in 100 mM Tris at pH 8.4. The protein- cetyl alcohol complex crystallizes in space group P2(1), with unit-cell par ameters a = 47.9, b = 49.7, c = 50.3 Angstrom, beta = 110.1 degrees. With t wo molecules in the asymmetric unit, the V-M is 2.15 Angstrom (3) Da(-1) an d the solvent content is 42%. A complete data set has been collected at 1.6 Angstrom resolution on beamline ID14-2 (ESRF, Grenoble). Se-Met expression has been performed with a view to solving the CSP2 structure with MAD data collection using the Se absorption edge.