X-ray Structure and Ligand Binding Study of a Moth Chemosensory Protein

Abstract

Two classes of highly soluble and very abundant proteins of ϳ150 amino acids have been detected in sensilla of Lepidoptera, both containing 6 conserved cysteines forming three disulfide bridges. The first class, that of GOBPs, 1 is equally distributed in both sexes, whereas the second class, that of PBPs, is mainly present in males (1). A third class of small proteins (average M r 13,000) has been identified in antennae from Drosophila melanogaster and in antennae and several sensorial organs (tarsi, labrum) from a wide range of species of the insect order (2-11). These proteins have been proposed to be involved in CO 2 detection (3), in chemical signal transmission in regenerating legs (5), or in chemo-perception (either olfaction or taste (9, 12)), and they were therefore called chemosensory proteins (CSPs). CSPs are shorter (110 -115 amino acids) than PBP or GOBP, contain only 4 conserved cysteines forming two disulfide bridges (9), and share no sequence homology with them.

Moth chemosensory protein exhibits drastic conformational changes and cooperativity on ligand binding

“…Finally, both tryptophans have their fluorescence modified on ligand binding. This observation is in agreement with the CSPMbraA6 x-ray complex structure, in which each of the tryptophans is close to the ligands, which is not the case for the 1:1 model (12).…”

“…Based on the fluorescence and NMR experiments, CSPMbraA6 was crystallized in the presence of BrC12OH, yielding two new crystal forms as compared with the apo-protein crystal forms 1 and 2 (12). The structure of the new crystal form 3 could not be solved by molecular replacement with the apo-protein coordinates, but could be solved by using single wavelength anomalous diffraction at the bromine edge.…”

“…A narrow channel starting from the surface region extends 14 Å within the core of the protein. This channel seemed suitable for binding alkyl compounds, a hypothesis that has been tested by using tryptophan fluorescence quenching with bromo-alkyl alcohols or acids (12). Here, we report the x-ray structure of CSPMbraA6 in complex with a surrogate ligand, 12-bromo-dodecanol (BrC12OH).…”

“…We have, therefore, initiated a structural and biophysical study of CSPs to explore their role in ligand transport and signal transduction. We have reported that the unbound CSPMbraA6 is remarkably different from PBP, either unbound or bound, and displays an original fold (12). Helices A and B as well as helices D and E form two V-shaped structures 12 Å apart, whereas helix C is perpendicular and in between them (Fig.…”

Comparing the Expression of Olfaction-Related Genes in Gypsy Moth (Lymantria dispar) Adult Females and Larvae from One Flightless and Two Flight-Capable Populations

“…Recent evidence suggests that OBPs are an adaptation to the detection of hydrophobic volatiles that became available as olfactory cues in the course of insect terrestrialization (Missbach et al, 2015); however, results in Drosophila suggest a different function for some OBPs (Larter et al, 2016). Structurally, insect OBPs and CSPs generally contain α-helical domains, but folded in two different patterns (Sandler et al, 2000;Lartigue et al, 2002;Tegoni et al, 2004).…”