title: Ligand-binding study of Anopheles gambiae chemosensory proteins.
abstract: Chemosensory proteins (CSPs) are a class of small proteins expressed only in arthropods and endowed with heterogeneous functions. Some of them are involved in chemical communications, others in development or other physiological roles. The numbers of CSPs in different species of insects range from 4 in Drosophila to at least 70 in locusts, whereas in other arthropods such as crustaceans and millipedes, only 2-3 very similar sequences have been reported in each species. We have expressed, in a bacterial system, 5 of the 8 CSPs predicted by the genome of the malaria mosquito Anopheles gambiae, 4 identified at the protein level (SAP1, SAP2, SAP3, and CSP3) and a fifth annotated as part of this work, obtaining the proteins with high yields and in their soluble forms. Purified CSPs have been used to study their ligand-binding properties, both using competitive binding assays and quenching of intrinsic tryptophan fluorescence, in order to get insights into their physiological functions. The agreement between the 2 sets of data supports the assumptions that the ligands, including the fluorescent reporter, bind within the core of the proteins. Their different affinities toward a set of pure chemicals suggest specific roles in chemical communication.
authors.affiliation: Department of Agriculture, Food and Environment, University of Pisa, Via del Borghetto, 80, 56124 Pisa, Italy.
authors.forename: Immacolata
authors.initials: I
authors.lastname: Iovinella
authors.forename: Francesco
authors.initials: F
authors.lastname: Bozza
authors.forename: Beniamino
authors.initials: B
authors.lastname: Caputo
authors.forename: Alessandra
authors.initials: A
authors.lastname: Della Torre
authors.forename: Paolo
authors.initials: P
authors.lastname: Pelosi
mesh_terms: D000818:Animals; D000852:Anopheles; D001665:Binding Sites; D005453:Fluorescence; D019476:Insect Proteins / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism*; D008024:Ligands; D014364:Tryptophan / Q000032:analysis / Q000737:chemistry
chemical_list: D019476:Insect Proteins; D008024:Ligands; D014364:Tryptophan
keywords: arthropods; chemical communication; protein expression; sensory appendage protein; tryptophan fluorescence