Thyroglobulin structure-function: Anilinonaphthalene sulfonate binding and the definition of nonpolar sites on native bovine thyroglobulin

Abstract

Summary Native bovine thyroglobulin has been shown by fluorescence titration and equilibrium dialysis to bind 6 moles of 1,8 anilinonaphthalene sulfonate (ANS) per mole of protein at pH 7.0 in 0.1 M sodium phosphate buffer. The average dissociation constant for this binding is 3 × 10 −5 M. Analysis of the binding data indicates significant cooperativity in the interaction with the reaction order, J, near 2. The binding of ANS to bovine thyroglobulin is accompanied by a blue shift in the ANS fluorescence maximum of near 50 nm and an increase in fluorescence yield of approximately 60 fold.