Hand-holding for retrohoming in a molecular diversity dance.

In bacterial systems, adaptive protein sequence changes can be mediated by diversity-generating retroelements in a process known as retrohoming. An accessory variability determinant (Avd), together with a reverse transcriptase (RT), is critically involved in this process. In this issue of Structure, Alayyoubi and colleagues describe the structure of Avd as a basis for interactions with RT that promote retrohoming.