Average orientation of aromatic residues in proteins determined from linear dichroism spectroscopy: A comparison of results on bovine γ-crystallins with X-ray data

Abstract

The structures of the two very closely related proteins, bovine gamma II- and gamma IVa-crystallin have been studied by means of near-ultra-violet linear dichroism spectroscopy on squeezed polyacrylamide gel systems. The crystallin spectra are discussed in terms of the spectra of the aromatic chromophores present in these proteins and provide detailed information on the average orientation of these residues in the proteins. A comparison of our results with information based on crystallographic X-ray experiments shows excellent agreement, reflecting even some of the minor differences between the two proteins studied. Since linear dichroism measurements as performed here take a few days only, and can be done on most aqueous protein solutions, linear dichroism spectroscopy may give a valuable contribution to structural studies on proteins.