Membrane Binding of Different Water-Soluble Protein Conformers: Effect on Protein Structure and Stability

Abstract

There is a large group of proteins which, although water-soluble, during the course of their action interact with plasma or intracellular membranes. The transition from the water-soluble to the membrane-bound state is accompanied by a rearrangement of the protein structure (1). A detailed characterization of this rather complex process is of particular importance to unravel the problem of protein folding in membrane environments. We present data on the association of different confonners of α-lactalbumin(αLA) with model membranes. This secretory protein binds a single Ca²⁺ ion, which stabilizes its structure, and contains four disulfide bonds, offering the oportunity to study the association of stable reduction intermediates with membranes. By using infrared spectroscopy, fluorescence spectroscopy and circular dichroism, we have characterized this structural transition.