STANDARD CONFORMATIONS FOR THE CANONICAL STRUCTURES OF IMMUNOGLOBULINS

A comparative analysis of the main-chain conformation of the L1, L2, L 3, H1 and H2 hypervariable regions in 17 immunoglobulin structures tha t have been accurately determined at high resolution is described. Thi s involves 79 hypervariable regions in all. We also analysed a part of the H3 region in 12 of the 15 V-H domains considered here. On the bas is of the residues at key sites the 79 hypervariable regions can be as signed to one of 18 different canonical structures. We show that 71 of these hypervariable regions have a conformation that is very close to what can be defined as a ''standard'' conformation of each canonical structure. These standard conformations are described in detail. The o ther eight hypervariable regions have small deviations from the standa rd conformations that, in six cases, involve only the rotation of a si ngle peptide group. Most H3 hypervariable regions have the same confor mation in the part that is close to the framework and the details of t his conformation are also described here. (C) 1997 Academic Press Limi ted.