title: Innate immunity in a pyralid moth: functional evaluation of domains from a beta-1,3-glucan recognition protein.
abstract: Invertebrates, like vertebrates, utilize pattern recognition proteins for detection of microbes and subsequent activation of innate immune responses. We report structural and functional properties of two domains from a beta-1,3-glucan recognition protein present in the hemolymph of a pyralid moth, Plodia interpunctella. A recombinant protein corresponding to the first 181 amino-terminal residues bound to beta-1,3-glucan, lipopolysaccharide, and lipoteichoic acid, polysaccharides found on cell surfaces of microorganisms, and also activated the prophenoloxidase-activating system, an immune response pathway in insects. The amino-terminal domain consists primarily of an alpha-helical secondary structure with a minor beta-structure. This domain was thermally stable and resisted proteolytic degradation. The 290 residue carboxyl-terminal domain, which is similar in sequence to glucanases, had less affinity for the polysaccharides, did not activate the prophenoloxidase cascade, had a more complicated CD spectrum, and was heat-labile and susceptible to proteinase digestion. The carboxyl-terminal domain bound to laminarin, a beta-1,3-glucan with beta-1,6 branches, but not to curdlan, a beta-1,3-glucan that lacks branching. These results indicate that the two domains of Plodia beta-1,3-glucan recognition protein, separated by a putative linker region, bind microbial polysaccharides with differing specificities and that the amino-terminal domain, which is unique to this class of pattern recognition receptors from invertebrates, is responsible for stimulating prophenoloxidase activation.
authors.affiliation: Department of Biochemistry, Kansas State University, Manhattan, Kansas 66506, USA.
authors.forename: Jeffrey A
authors.initials: JA
authors.lastname: Fabrick
authors.forename: James E
authors.initials: JE
authors.lastname: Baker
authors.forename: Michael R
authors.initials: MR
authors.lastname: Kanost
mesh_terms: D000818:Animals; D002942:Circular Dichroism; D018076:DNA, Complementary / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004591:Electrophoresis, Polyacrylamide Gel; D004789:Enzyme Activation; D004926:Escherichia coli / Q000378:metabolism; D017353:Gene Deletion; D005936:Glucans / Q000737:chemistry*; D007113:Immunity, Innate; D008070:Lipopolysaccharides / Q000737:chemistry; D009036:Moths; D011134:Polysaccharides / Q000737:chemistry; D011485:Protein Binding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry; D020349:Surface Plasmon Resonance; D013682:Teichoic Acids; D013696:Temperature; D013997:Time Factors; D047071:beta-Glucans
chemical_list: D018076:DNA, Complementary; D005936:Glucans; D008070:Lipopolysaccharides; D011134:Polysaccharides; D011994:Recombinant Proteins; D013682:Teichoic Acids; D047071:beta-Glucans; C009900:lipoteichoic acid; C038459:curdlan; C033363:beta-1,3-glucan