Solution structure of the silkworm betaGRP/GNBP3 N-terminal domain reveals the mechanism for beta-1,3-glucan-specific recognition.
The beta-1,3-glucan recognition protein (betaGRP)/Gram-negative bacteria-binding protein 3 (GNBP3) is a crucial pattern-recognition receptor that specifically binds beta-1,3-glucan, a component of fungal cell walls. It evokes innate immunity against fungi through activation of the prophenoloxidase (proPO) cascade and Toll pathway in invertebrates. The betaGRP consists of an N-terminal beta-1,3-glucan-recognition domain and a C-terminal glucanase-like domain, with the former reported to be responsible for the proPO cascade activation. This report shows the solution structure of the N-terminal beta-1,3-glucan recognition domain of silkworm betaGRP. Although the N-terminal domain of betaGRP has a beta-sandwich fold, often seen in carbohydrate-binding modules, both NMR titration experiments and mutational analysis showed that betaGRP has a binding mechanism which is distinct from those observed in previously reported carbohydarate-binding domains. Our results suggest that betaGRP is a beta-1,3-glucan-recognition protein that specifically recognizes a triple-helical structure of beta-1,3-glucan.
Takahasi
Kiyohiro
K
Department of Structural Biology, Graduate School of Pharmaceutical Sciences, Hokkaido University, N-21, W-11, Kita-ku, Sapporo 001-0021, Japan.
Ochiai
Masanori
M
Horiuchi
Masataka
M
Kumeta
Hiroyuki
H
Ogura
Kenji
K
Ashida
Masaaki
M
Inagaki
Fuyuhiko
F
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D012831:Bombyx / Q000235:genetics* / Q000276:immunology; D002352:Carrier Proteins / Q000235:genetics* / Q000378:metabolism; D004252:DNA Mutational Analysis; D007113:Immunity, Innate / Q000235:genetics*; D019476:Insect Proteins / Q000235:genetics* / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011485:Protein Binding; D011487:Protein Conformation; D017510:Protein Folding; D016415:Sequence Alignment; D047071:beta-Glucans / Q000378:metabolism
D002352:Carrier Proteins; D019476:Insect Proteins; C405332:beta-1,3-glucan recognition protein, insect; D047071:beta-Glucans; C033363:beta-1,3-glucan