The use of 1-anilino-8-naphthalene sulfonate as fluorescent probe for conformational studies on ribulose-1,5-bisphosphate carboxylase.

The influence of Mg2+ ions and temperature on the structure of the enzyme ribulose-1,5-bisphosphate carboxylase was investigated using the fluorescent probe 1-anilino-8-naphthalene sulfonate (ANS). The binding of ANS to the enzyme molecule caused a significant increase of fluorescence emission which was further enhanced by the addition of Mg2+. The temperature dependence of the fluorescence emission indicated a conformational change of the enzyme between 12 and 24 degrees C. The Mg2+ and the temperature effects were additive. ANS itself did not change the conformation of the enzyme. The influence of the substrates carbon dioxide and ribulose-1,5-bisphosphate, and the effect of the pH of the medium and of a sulfhydryl reducing reagent on fluorescence emission were analysed.