Binding of diarrheic shellfish poisoning toxins to okadaic acid binding proteins purified from the sponge Halichondria okadai.
Okadaic acid (OA) and dinophysistoxin-1 (DTX1) cause diarrheic shellfish poisoning. This article examines the biochemical interactions of the two toxins with novel okadaic acid binding proteins (OABPs) 2.1 and 2.3, originally isolated from the marine sponge Halichondria okadai. First, recombinant OABPs 2.1 and 2.3 were expressed in Escherichia coli BL21 (DE3) cells. Binding assays using [24-(3)H]OA and the recombinant OABP 2.1 or 2.3 demonstrated the dissociation constant K(d) of 1.30±0.56 nM and 1.54±0.35 nM, respectively. Binding of [24-(3)H]okadaic acid to recombinant OABP2.1 was almost equally replaced with OA and DTX1. OA-induced cytotoxicity in mouse leukemia P388 cells was inhibited in the presence of the recombinant OABPs 2.1 and 2.3 with an EC(50) of 92±8.4 nM and 87±13 nM, respectively. These results suggest that the blockage of OA-induced cytotoxicity by OABPs 2.1 and 2.3 may be involved in regulating symbiotic relationships present in the sponge H. okadai.
Konoki
Keiichi
K
Graduate School of Agricultural Science, Tohoku University, Tsutsumidori-Amamiyamachi 1-1, Aoba-ku, Sendai 981-8555, Japan. konoki@biochem.tohoku.ac.jp
Saito
Kaori
K
Matsuura
Hiroki
H
Sugiyama
Naoyuki
N
Cho
Yuko
Y
Yotsu-Yamashita
Mari
M
Tachibana
Kazuo
K
D000818:Animals; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D008387:Marine Toxins / Q000378:metabolism / Q000633:toxicity*; D051379:Mice; D019319:Okadaic Acid / Q000633:toxicity* / Q000031:analogs & derivatives; D011161:Porifera; D011485:Protein Binding; D011714:Pyrans / Q000378:metabolism; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism
D002352:Carrier Proteins; D008387:Marine Toxins; D011714:Pyrans; D011994:Recombinant Proteins; D019319:Okadaic Acid; C051904:dinophysistoxin 1