THE CORE DOMAIN OF RETROTRANSPOSON INTEGRASE IN HORDEUM - PREDICTED STRUCTURE AND EVOLUTION

Propagation of long terminal repeat (LTR)-bearing retrotransposons and retroviruses requires integrase (LN, EC 2.7.7.-), encoded by the retr oelements themselves, which mediates the insertion of cDNA copies back into the genome. An active retrotransposon family, BARE-1, comprises similar to 7% of the barley (Hordeum vulgare subsp. vulgare) genome. W e have generated models for the secondary and tertiary structure of BA RE-I IN and demonstrate their similarity to structures for human immun odeficiency virus 1 and avian sarcoma virus INs. The IN core domains w ere compared for 80 clones from 28 Hordeum accessions representative o f the diversity of the genus. Based on the structural model, variation s in the predicted, aligned translations from these clones would have minimal structural and functional effects on the encoded enzymes. This indicates that Hordeum retrotransposon IN has been under purifying se lection to maintain a structure typical of retroviral INs. These repre sent the first such analyses for plant INs.