Secreted effector that acts as an elicitor of hypersensitive response (HR) specifically on plants carrying defense protein Rpi-blb2 (PubMed:19794118). Enhances P.infestans colonization of Nicotiana benthamiana leaves (PubMed:30329083). Interacts with, and subsequently prevents secretion into the apoplast of the host papain-like cysteine protease C14, thus promoting virulence by interfering with the execution of host defenses (PubMed:22143776). Associates with calmodulin at the host plasma membrane to interfere with plant defense-associated calcium signaling in hosts (PubMed:30984224). Interacts with the host papain-like cysteine protease C14 (PubMed:22143776). Interacts with the host calmodulin (PubMed:30984224). AVRblb2 localization is essential for its virulence function but not for its avirulence activity. Expression is induced during host plant infection. The RxLR-dEER motif acts to carry the protein into the host cell cytoplasm through binding to cell surface phosphatidylinositol-3-phosphate (Probable). The motif is not required for perception by defense protein Rpi-blb2 (PubMed:19794118). The 8 residues at the C-terminus (residues 93 to 100) are required for the correct subcellular location at the cell periphery or around haustoria, the ability to enhance P.infestans growth, the association with C14 protease, and apoplastic C14 accumulation. The amino acids 78-82 in the C-terminal region of are important for binding to host calmodulin. The Avrblb2 protein of Phytophthora infestans is a polymorphic member of the RXLR class of secreted effectors. Especially, the polymorphic amino acid at position 69 is critical for activation of Rpi-blb2 hypersensitivity. The Avrblb2 homologs that are recognized by Rpi-blb2 have 'Val-69', 'Ala-69', or 'Ile-69', whereas the those that are not recognized have 'Phe-69'. Belongs to the RxLR effector family.