P-247 - In silico structural analysis of the interaction between the TMV helicase domain and the TIR domain of the N resistance protein involves conformational changes in both proteins

Resistance gene products interact directly or indirectly with their elicitors. In the case of N gene-mediated resistance to infection by TMV in tobacco, the TIR domain of the N protein (amino acids 10-192) was shown to interact with the helicase (HEL) domain (aa 801-1116) of the TMV 126-kDa replication-associated protein. The nature of the structural interactions that occur between the HEL and TIR domains was not known. We have examined the structures of both proteins and modeled their interactions using AlphaFold2. The structures obtained for N-TIR and HEL were similar to other TIR domains, and the tomato mosaic virus HEL domain, respectively, both solved by crystallography. The interactions of the TMV HEL and N-TIR examined before and after molecular dynamic simulation showed changes in the structure of both proteins occurred after interaction, with the loss of the small, second beta-sheet and part of the C-terminal alpha-helix in the TIR domain, after the simulation. Seven amino acids of both the TIR domain (between R96 and Q186) and the HEL domain (R803 to D958) were involved in eight interactions before the simulation, while nine TIR amino acids (W10, plus K98 to D192) of TIR and 11 amino acids (V802 to E957) of HEL were involved in 12 interactions afterwards. The limited interactions suggest that the TIR-HEL complex may not be very stable in the absence of other plant proteins is consistent with in various vitro vs. in vivo studies.