Solution Structure of a Chemosensory Protein from the Desert Locust Schistocerca gregaria^,

Abstract

Chemical stimuli, generally constituted by small volatile organic molecules, are extremely important for the survival of different insect species. In the course of evolution, insects have developed very sophisticated biochemical systems for the binding and the delivery of specific semiochemicals to their cognate membrane-bound receptors. Chemosensory proteins (CSPs) are a class of small soluble proteins present at high concentration in insect chemosensory organs; they are supposed to be involved in carrying the chemical messages from the environment to the chemosensory receptors. In this paper, we report on the solution structure of CSPsg4, a chemosensory protein from the desert locust Schistocerca gregaria, which is expressed in the antennae and other chemosensory organs. The 3D NMR structure revealed an overall fold consisting of six alpha-helices, spanning residues 13-18, 20-31, 40-54, 62-78, 80-90, and 97-103, connected by loops which in some cases show dihedral angles typical of beta-turns. As in the only other chemosensory protein whose structure has been solved so far, namely, CSP from the moth Mamestra brassicae, four helices are arranged to form a V-shaped motif; another helix runs across the two V's, and the last one is packed against the external face. Analysis of the tertiary structure evidenced multiple hydrophobic cavities which could be involved in ligand binding. In fact, incubation of the protein with a natural ligand, namely, oleamide, produced substantial changes to the NMR spectra, suggesting extensive conformational transitions upon ligand binding.

Diversity, abundance, and sex-specific expression of chemosensory proteins in the reproductive organs of the locust Locusta migratoria manilensis

“…A model of the protein (Figure 7), built on the solution structure of S. gregaria CSP1 as a template (Tomaselli et al , 2006 ), is consistent with the observed good affinity of the protein for unbranched long-chain acids and analogues, in particular with the unsaturated oleic and linoleic acid. The two lysine residues, Lys46 and Lys89, located at the entrance of the binding cavity, could strongly interact with the carboxy groups of the fatty acids.…”

“…The threedimensional (3D) structure is made of six α -helical domains arranged in a compact folding and enclosing a binding cavity for hydrophobic organic compounds (Lartigue et al , 2002 ;Tomaselli et al , 2006 ;Jansen et al , 2007 ). Several CSPs have been described in the lymph of olfactory and taste sensilla in different insect species.…”

Structure of Bombyx mori chemosensory protein 1 in solution

“…CSPMbraA6 is localized in antennae and proboscis in M. brassicae (Bohbot et al, 1998;Nagnan-Le Meillour et al, 2000; JacquinJoly et al, 2001) and CSPsg4 is localized in antenna and other chemosensory organs in S. gregaria (Angeli et al, 1999). Both proteins have a similar structure consisting of six α-helices forming two parallel arches closed at the bottom by a helix and forming a ligand binding pocket able to accomodate long carbon chains of fatty acids (Campanacci et al, 2001(Campanacci et al, , 2003Lartigue et al, 2002;Mosbah et al, 2003;Tomaselli et al, 2006).The genome of B. mori has been sequenced (Mita et al, 2004;Xia et al, 2004). In B. mori, 15 CSPs have been identified (Gong et al, 2007).…”

Unique function of a chemosensory protein in the proboscis of two Helicoverpa species

“…The motif of four cysteines at conserved positions is the signature of this class of protein (Picimbon, 2003;Wanner et al, 2004;Vogt, 2005;Pelosi et al, 2006). The three-dimensional structure of CSPs, known for only three members of the family [Mamestra brassicae (Lartigue et al, 2002), Bombyx mori (Jansen et al, 2007) and Schistocerca gregaria (Tomaselli et al, 2006)], is made of six α-helical domains arranged in a highly compact and stable structure that contains a binding cavity lined with hydrophobic residues. Some members of the family are present at high concentration in the lymph of chemosensilla, located on the sensory organs of insects (Angeli et al, 1999;Jin et al, 2005).…”