<i>In Silico</i> Structural Analysis of the Grapevine Serine Protease VviSBT4.19 Involved in Defense against <i>P. viticola</i>

Grapevine pathogens, such as <i>Plasmopara viticola</i>, a downy mildew disease-causing agent, pose a significant threat to grape and wine production worldwide. Molecular details are needed on how tolerant grapevine species recognize and mount a successful defense response against this pathogen. We have identified the important role of grapevine subtilase VviSBT4.19; however, without a reliable structural model, we have a limited understanding of protease activity modulation by <i>P. viticola</i>. Here, we built a consensus computational model of this protein and performed constant-pH MD simulations to assess its overall structural stability. We identified Ser419 as the key residue in autocatalytic processing and demonstrated that its S419N mutation produces a stable, active protease with a reduced autocatalytic activity. This work provides the first reliable structural model of VviSBT4.19, offering crucial insights into its function and regulation and opening new avenues for engineering enhanced disease resistance in grapevine cultivars.