Interaction of biotin with streptavidin: thermostability and conformational changes upon binding

GONZÁLEZ M.,; BAGATOLLI L.A.,; ECHABE I,; ARRONDO J.L,; ARGARAÑA CE; CANTOR C.R.,; FIDELIO G.D.,

AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC

Año: 1997 vol. 272 p. 11288 - 11288

he effect of biotin binding on streptavidin (STV)structure and stability was studied using differential scanning calorimetry, Fourier transform infrared spectroscopy (FT-IR), and fluorescence spectroscopy. Biotin increases the midpoint temperature Tm, of thermally induced denaturation of STV from 75 °C in unliganded protein to 112 °C at full ligand saturation. The cooperativity of thermally induced unfolding of STV changes substantially in presence of biotin. Unliganded STV monomer has at least one domain that unfolds independently. The dimer bound to biotin undergoes a single coupled denaturation process. Simulations of thermograms of STV denaturation that take into account only the thermodynamic effects of the ligand with a Ka ;1015 reproduce the ehavior observed, but the estimated values of Tm are 15?20°C lower than those experimentally determined. This increased stability is attributed to an enhanced cooperativity of the thermal unfolding of STV. The increment in the cooperativi