The PenV vacuolar membrane protein that controls penicillin biosynthesis is a putative member of a subfamily of stress-gated transient receptor calcium channels

The penV gene of Penicillium chrysogenum, involved in the control of penicillin biosynthesis, encodes a large-size (832 amino acids) putative transient receptor potential (TRP) ion channel that might interact with different ligands and other proteins. It belongs to a novel class of stress-gated TRP channels similar to the calcium transporter CSC type TRP of Arabidopsis thaliana and yeasts. These TRP proteins contains eleven and twelve transmembrane domains in yeasts and fungi, respectively, with one large interdomain loop and a C-terminal unstructured region that allows the interaction with ligands. The physiological action of many TRPs is mediated by calcium signalling. Ca2+ is released from the vacuoles into the cytosol in response to external stressing factors. PenV increases expression of the two late genes of penicillin biosynthesis (pcbC and penDE) probably by a calcium signalling cascade. The possible involvement of TRPs in the sensing of ligands or in interaction with other proteins, e.g. calmodulin, is a novel and interesting aspect of regulation of the biosynthesis of secondary metabolites in fungi.