Open AccessInteractions of Colipase with Bile Salt Micelles
Author(s) -
SARI Hélène,
ENTRESSANGLES Bernard,
DESNUELLE Pierre
Publication year - 1975
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1975.tb02406.x
Subject(s) - micelle , colipase , salt (chemistry) , chemistry , salt bridge , biochemistry , enzyme , organic chemistry , aqueous solution , lipase , pancreatic lipase , mutant , gene
The finding reported in the preceding paper that colipase is able to bind one sodium taurodeoxycholate micelle per molecule was confirmed by dialysis and spectrophotometry. Dialysis in the presence of labelled sodium taurodeoxycholate provided a direct qualitative proof of taurodeoxycholate binding to colipase. This binding was found to occur only above the critical micelle concentration. But, dialysis did not give any information about the composition of the associations, because equilibrium was not attained at the end of the assays. Addition of sodium taurodeoxycholate above the critical micelle concentration was also observed to induce a strong perturbation of the ultraviolet spectrum of one or several of the three tyrosines of colipase. The variation of the perturbation as a function of sodium taurodeoxycholate concentration was consistent with the binding of a single micelle to colipase. The dissociation constant calculated in “micelle molarity” was approximately 1 × 10 ‐4 M. The colipase‐bile salt micelle association can fix one molecule of lipase to form a ternary complex which represents an interesting model of a protein‐protein interaction mediated by an organized lipid structure. The ternary complex is probably also a model for lipase‐substrate interactions in the presence of an amphipath.