An azurocidin-like protein is induced in Trichoplusia ni larval gut cells after bacterial challenge.
Trichoplusia ni immune genes up-regulated in response to bacterial infection have been isolated using differential display polymerase chain reaction. Here we report the cloning and characterisation of a gut-specific immune gene encoding an azurocidin-like protein. The deduced protein is 317 amino acid residues long with a hydrophobic C-terminus and a predicted 17-residue signal peptide. The mature T. ni protein shows 30% identity to human azurocidin, an antibacterial protein. Like azurocidin, the T. ni protein contains two amino acid substitutions in the active site triad normally present in serine proteases. The T. ni protein was synthesised with a six-histidine C-terminal extension using the baculovirus expression system. Sequencing of the recombinant azurocidin-like protein confirmed the predicted cleavage of the signal peptide. Northern blots show that T. ni azurocidin-like protein is expressed solely in the larval gut and that expression is up-regulated by injecting or feeding bacteria. Expression reaches its highest level at 10 h after bacteria injection.
Kang
Daiwu
D
Department of Microbiology, Stockholm University, S-106 91, Stockholm, Sweden.
Lundström
Annika
A
Liu
Gang
G
Steiner
Håkan
H
D000595:Amino Acid Sequence; D000818:Animals; D023181:Antimicrobial Cationic Peptides; D016367:Baculoviridae / Q000235:genetics; D001483:Base Sequence; D001798:Blood Proteins / Q000096:biosynthesis / Q000235:genetics*; D015152:Blotting, Northern; D015139:Blotting, Southern; D002352:Carrier Proteins / Q000096:biosynthesis / Q000235:genetics*; D003001:Cloning, Molecular; D004269:DNA, Bacterial / Q000235:genetics; D016972:Enterobacter cloacae / Q000276:immunology; D020869:Gene Expression Profiling; D007915:Lepidoptera / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000235:genetics; D017386:Sequence Homology, Amino Acid; D015854:Up-Regulation / Q000276:immunology
C062991:AZU1 protein, human; D023181:Antimicrobial Cationic Peptides; D001798:Blood Proteins; D002352:Carrier Proteins; D004269:DNA, Bacterial; D011994:Recombinant Proteins