Subgroups of variable region genes of beta chains of T-cell receptors for antigen.

The beta-chain variable regions of 6 human, 21 mouse, and 1 rabbit T-cell receptors for antigen, including two pairs of duplicates, have been classified into two subgroups. Subgroup I has an invariant Phe at residue 65 and a salt bridge can be formed between the Asp at position 86 and the 11 Arg, 2 Lys, and 1 His residues at position 64. In one instance Tyr replaces Asp at position 86 so that a salt bridge cannot be formed with the Lys at position 64. Subgroup II has an invariant Tyr at residue 65; 8 chains have Gly and 3 have Ala at position 63. These 3 have Asp at position 64. Those with Gly-63 cannot form a salt bridge in this region of the beta chain. The 3 with Asp-64 have Arg at position 86, can form a reverse salt bridge, and could constitute a third subgroup. The relation of these findings to functional parameters in beta chains of the T-cell receptors for antigen deserves further study. The use of variability plots on the assumption that the beta chains are a single population may be misleading for the variable region. Most of the variability in the expressed beta chains would be created by variable-diversity-joining assortment, junctional diversity, and the possible insertion of N sequences.