TY - JOUR
T1 - pH regulates pore formation of a protease activated Vip3Aa from Bacillus thuringiensis
AU - Kunthic, Thittaya
AU - Watanabe, Hirokazu
AU - Kawano, Ryuji
AU - Tanaka, Yoshikazu
AU - Promdonkoy, Boonhiang
AU - Yao, Min
AU - Boonserm, Panadda
N1 - Funding Information:
This work was supported by the Royal Golden Jubilee Ph.D. Program, Thailand (to TK), the Thailand Research Fund [grant number IRG5780009 ] and Mahidol University, Thailand (to PB), JST PRESTO [grant number JPMJPR1517 ], Grant-in-Aid for Scientific Research [grant numbers 24000011, 16H00748, and 26291008] from the Ministry of Education, Japan (to YT).
Publisher Copyright:
© 2017 Elsevier B.V.
PY - 2017/11
Y1 - 2017/11
N2 - Vip3Aa insecticidal protein is produced from Bacillus thuringiensis and exerts a broad spectrum of toxicity against lepidopteran insect species. Although Vip3Aa has been effectively used as part of integrated pest management strategies, the mechanism of the toxin remains unclear. Here, we investigated the effect of pH in a range from 5.0 to 10.0 on the pore-forming activity of the trypsin activated Vip3Aa (actVip3Aa) by in vitro pore-forming assays. Based on calcein release assay, actVip3Aa could permeabilize the artificial neutral liposomes under all the pH tested, except pH 10.0. The maximum membrane permeability of actVip3Aa was detected at pH 8.0 and the permeability decreased and abolished when exposing to acidic and alkaline conditions, respectively. The planar lipid bilayer experiment revealed that actVip3Aa formed ion channels at pH 5.0–8.0 but no current signals were detected at pH 10.0, consistent with the observation from calcein release assay. The toxin formed ion channels with a diameter of 1.4 nm at pH 8.0 and pore size was gradually decreased when reducing the pH. This study provided a view of the molecular mechanism of Vip3Aa by which the pore-forming activity is regulated by pH.
AB - Vip3Aa insecticidal protein is produced from Bacillus thuringiensis and exerts a broad spectrum of toxicity against lepidopteran insect species. Although Vip3Aa has been effectively used as part of integrated pest management strategies, the mechanism of the toxin remains unclear. Here, we investigated the effect of pH in a range from 5.0 to 10.0 on the pore-forming activity of the trypsin activated Vip3Aa (actVip3Aa) by in vitro pore-forming assays. Based on calcein release assay, actVip3Aa could permeabilize the artificial neutral liposomes under all the pH tested, except pH 10.0. The maximum membrane permeability of actVip3Aa was detected at pH 8.0 and the permeability decreased and abolished when exposing to acidic and alkaline conditions, respectively. The planar lipid bilayer experiment revealed that actVip3Aa formed ion channels at pH 5.0–8.0 but no current signals were detected at pH 10.0, consistent with the observation from calcein release assay. The toxin formed ion channels with a diameter of 1.4 nm at pH 8.0 and pore size was gradually decreased when reducing the pH. This study provided a view of the molecular mechanism of Vip3Aa by which the pore-forming activity is regulated by pH.
KW - Bacillus thuringiensis
KW - Ion channels
KW - Membrane insertion
KW - Planar lipid bilayers
KW - Pore formation
KW - Vip3Aa
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U2 - 10.1016/j.bbamem.2017.08.018
DO - 10.1016/j.bbamem.2017.08.018
M3 - Article
C2 - 28865796
AN - SCOPUS:85029142807
SN - 0005-2736
VL - 1859
SP - 2234
EP - 2241
JO - Biochimica et Biophysica Acta - Biomembranes
JF - Biochimica et Biophysica Acta - Biomembranes
IS - 11
ER -