Open AccessComparison of coligenoid formation by B subunits of porcine and human Escherichia coli heat‐labile enterotoxins
Author(s) -
Tsuji Takao,
Honda Takeshi,
Miwatani Toshio,
Miyama Akio
Publication year - 1990
Publication title -
fems microbiology letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.899
H-Index - 151
eISSN - 1574-6968
pISSN - 0378-1097
DOI - 10.1111/j.1574-6968.1990.tb04248.x
Subject(s) - monomer , long term potentiation , protein subunit , chemistry , enterotoxin , biochemistry , escherichia coli , dissociation (chemistry) , biophysics , stereochemistry , biology , organic chemistry , receptor , gene , polymer
A hybrid B subunit (coligenoid) of heat‐labile enterotoxin could not be made from human heat‐labile enterotoxin B subunit(LTh‐B) and porcine LTp‐B subunit(LTp‐B). LTp‐B monomer was able to form coligenoid by reassociation with homologous LTp‐B monomer, but not with heterogeneous LTh‐B monomer and vice versa. The dissociation of both coligenoids into monomers by SDS treatment occurred in a time‐dependent manner, but the dissociation of LTh‐B colligenoid was faster than that of LTp‐B coligenoid. The association of LTp‐B monomer is tighter than that of LTh‐B monomer. The p I values of LTp‐B coligenoid, LTp‐B monomer and denatured LTp‐B monomer were similar at 9.6–9.8, while the p I values of LTh‐B coligenoid, LTh‐B monomer and denatured LTh‐B monomer were determined as 5.6–5.8, 9.2–9.6 and 9.2–9.6, respectively. All the ionic amino acids of LTp‐B exist on the coligenoid surface. The difference in p I values between LTh‐B coligenoid and LTh‐B monomer suggests that some basic amino acids are located within the LTh‐B coligenoid complex, but are exposed in the LTh‐B monomer. These data suggest that the 4 amino acid substitutions between LTh‐B and LTp‐B result in a three dimensional structure difference and a less stable formation of LTh‐B coligenoid compared to LTp‐B coligenoid.