Beauvericin synthetase contains a calmodulin binding motif in the entomopathogenic fungus Beauveria bassiana

Beauvericin is a mycotoxin which has insecticidal, anti-microbial, anti-viral and anti-cancer activities. Beauvericin biosynthesis is rapidly catalyzed by the beauvericin synthetase (BEAS) in Beauveria bassiana. Ca2+ plays crucial roles in multiple signaling pathways in eukaryotic cells. These Ca2+ signals are partially decoded by Ca2+ sensor calmodulin (CaM). In this report, we describe that B. bassiana BEAS (BbBEAS) can interact with CaM in a Ca2+-dependent manner. A synthetic BbBEAS peptide, corresponding to the putative CaM-binding motif, formed a stable complex with CaM in the presence of Ca2+. In addition, in vitro CaM-binding assay revealed that the His-tagged BbBEAS (amino acids 2421–2538) binds to CaM in a Ca2+-dependent manner. Therefore, this work suggests that BbBEAS is a novel CaM-binding protein in B. bassiana.