recombination attachment site attR The integration reaction is catalyzed by the integrase and, as a result of the site-specific recombination, will lead to direct repeats (typically between 10 and 60 bp) forming on either end of the integrated element, that are nownamed attL (left end) and attR (right end). Meng LIU (Mia), Oliver He https://academic.oup.com/femsre/article/41/4/512/3089980