Relative orientation of close-packed β-pleated sheets in proteins

Relative orientation of close-packed β-pleated sheets in proteins

Cyrus Chothia*,† and
Joël Janin‡

^*William Ramsay, Ralph Foster and Christopher Ingold Laboratories, University College London, Gower Street, London WC1E 6BT, England
^†Medical Research Council Laboratory of Molecular Biology, Hills Road, Cambridge CB2 2QH, England
^‡Unité de Biochimie Cellulaire, Départment de Biochimie et Génétique Moleculaire, Institut Pasteur, 28 rue du Docteur Roux, 75724 Paris Cedex 15, France

Abstract

When β-pleated sheets pack face to face in proteins, the angle between the strand directions of the two β-sheets is observed to be near -30°. We propose a simple model for β-sheet-to-β-sheet packing in concanavalin A, plastocyanin, γ-crystallin, superoxide dismutase, prealbumin, and the immunoglobin fragment V_REI. This model shows how the observed relative orientation of two packed β-sheets is a consequence of (i) the rows of side chains at the interface being approximately aligned and (ii) the β-sheet having a right-handed twist. The special amino acid composition of residues at the β-sheet-to-β-sheet interfaces makes the contact surfaces essentially smooth and hydrophobic.