N-terminal GNBP homology domain of Gram-negative binding protein 3 functions as a beta-1,3-glucan binding motif in Tenebrio molitor.
The Toll signalling pathway in invertebrates is responsible for defense against Gram-positive bacteria and fungi, leading to the expression of antimicrobial peptides via NF-kappaB-like transcription factors. Gram-negative binding protein 3 (GNBP3) detects beta-1,3-glucan, a fungal cell wall component, and activates a three step serine protease cascade for activation of the Toll signalling pathway. Here, we showed that the recombinant N-terminal domain of Tenebrio molitor GNBP3 bound to beta-1,3-glucan, but did not activate down-stream serine protease cascade in vitro. Reversely, the N-terminal domain blocked GNBP3-mediated serine protease cascade activation in vitro and also inhibited beta-1,3-glucan-mediated antimicrobial peptide induction in Tenebrio molitor larvae. These results suggest that the N-terminal GNBP homology domain of GNBP3 functions as a beta-1,3-glucan binding domain and the C-terminal domain of GNBP3 may be required for the recruitment of immediate down-stream serine protease zymogen during Toll signalling pathway activation.
Lee
Hanna
H
National Research Laboratory of Defense Proteins, College of Pharmacy, Pusan National University, Busan 609-735, Korea.
Kwon
Hyun-Mi
HM
Park
Ji-Won
JW
Kurokawa
Kenji
K
Lee
Bok Luel
BL
D020816:Amino Acid Motifs; D000818:Animals; D023181:Antimicrobial Cationic Peptides / Q000378:metabolism; D004926:Escherichia coli; D019476:Insect Proteins / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000302:isolation & purification; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D013712:Tenebrio / Q000378:metabolism*; D047071:beta-Glucans / Q000378:metabolism*
D023181:Antimicrobial Cationic Peptides; D019476:Insect Proteins; D011994:Recombinant Proteins; D047071:beta-Glucans; C033363:beta-1,3-glucan