A SKEWED DISTRIBUTION OF AMINO-ACIDS AT RECOGNITION SITES OF THE HYPERVARIABLE REGION OF IMMUNOGLOBULINS

Antibody binding site are formed by six hypervariable regions or compl ementarity determining regions (CDRs). The CDRs, three from the heavy chain and three from the light chain, are known as hypervariable segme nts and provide a surface complementary to that of the epitope. In rec ent work it was found that the amino acids in these positions fulfill different functions: Some play a structural role and others are involv ed in the specificity-determining function. It is reported here that t he frequency of amino acids at hypervariable sites is skewed. By means of an informational algorithm, key physicochemical attributes of the dominant residues were identified for some of those sites. The results for about 1,500 antibodies suggest that approximately 35% of sites in volved in the recognition process require only general properties such as composition, volume, and bulk or hydrogen bonding which are satisf ied by a small set of amino acids instead of any one particular comple mentary amino acid.