The structure of β-lactoglobulin and its similarity to plasma retinol-binding protein

M. Z. Papiz, Edinburgh Napier University
L. Sawyer, Edinburgh Napier University
E. E. Eliopoulos, University of Leeds
A. C.T. North, University of Leeds
J. B.C. Findlay, University of Leeds
R. Sivaprasadarao, University of Leeds
T. A. Jones, Uppsala Universitet
M. E. Newcomer, Uppsala Universitet
P. J. Kraulis, Uppsala Universitet

Abstract

Since its first isolation1, bovine β-lactoglobulin (BLG) has been an enigma: Although it is abundant in the whey fraction of milk, its function is still not clear. The results of the many physicochemical studies on the protein need a structural interpretation. We report here the structure of the orthorhombic crystal form of cow BLG at pH 7.6, at a resolution of 2.8 Å. It has an unusual protein fold, composed of two slabs of antiparallel β-sheet, which shows a remarkable similarity to plasma retinol-binding protein. A possible binding site for retinol in BLG has been identified by model-building. This suggests a role for BLG in vitamin A transport and we have discovered specific receptors for the BLG-retinol complex in the intestine of neonate calves. © 1986 Nature Publishing Group.