Crystal structure of rice APIP6 reveals a new dimerization mode of RING-type E3 ligases that facilities the construction of its working model

Abstract Ubiquitination is an important modification process in eukaryotic organisms, and ubiquitin ligase (E3) the most diversified component of this system. APIP6 (AvrPiz-t interacting protein 6) one E3s rice, involved recognition AvrPiz-t, effector from pathogen Magnaporthe oryzae , for initiation host defense against M. . However, structural detail how performs its function remains elusive. Here, we present crystal structure RING domain (i.e., E2-interaction domain) (APIP6-RING). APIP6-RING exists as a homodimer packing, solution vivo. consists β hairpin α helix, hairpins two molecules interact with each other novel ‘shoulder-to-shoulder’ mode to form sheet, also rendering homodimer. Hydrogen bonds play major role dimer formation APIP6-RING, while hydrophobic-intermolecular interactions are inconspicuous. Due interaction between RING-type E3 E2 generally conserved, constructed verified model APIP6-RING/E2 complex, proposed working E2, ubiquitin, substrate AvrPiz-t. Taken together, our research presents first plant simple that unreported dimerization manner, well APIP6.