Modeling-based identification of a Raptor-binding motif present in Arabidopsis ABA receptor PYL1

By employing molecular modeling of interaction simulation combined with a confirmatory yeast two-hybrid analysis, we identified the Raptor-binding region in an ABA receptor PYL1 protein of Arabidopsis. The region was a part of the C-terminal alpha-helix structure of the protein within which a phenylalanine and an aspartate in the sequence of FADTV are predicted to form critical interactions with the Raptor. Although the sequence deviates a little from the plant TOS consensus that we previously identified and defined (FSD [V/I]F) from AtS6Ks and its orthologues as well as AtATG13, the modeling data indicate that the sequence and its neighboring area are structurally capable of establishing the interaction with the Raptor in the same mode as those of other TOS motif-containing structures. This finding provides a new insight into the understanding of plant TOS motif, based upon which a putative Raptor-binding region in TAP46, another TOR substrate, is proposed.