Unveiling the 3D structure of phytoplasma effectors: A streamlined protocol for SAP11_CaPM expression and purification

SAP11-like proteins, a well-characterized class of phytoplasma effectors, are known to interact with TCP plant transcription factors, leading to significant changes in plant phenotype and metabolism. Understanding the molecular mechanisms underlying these interactions is essential. This study focuses on the expression and purification of the SAP11 effector of ‘Candidatus Phytoplasma mali’ (SAP11_CaPM) in Escherichia coli. The protocol includes the expression of the fusion protein with maltose binding protein for improved solubility and facilitated purification. Following affinity purification, the fusion protein was cleaved using factor Xa, and SAP11_CaPM was separated via cation exchange chromatography. This approach provides sufficiently pure protein quantity for nuclear magnetic resonance studies.