1.D.35 The Pore-forming Cyclic Lipodepsipeptide (Lipodepsipeptide) Family
Several lipodepsipeptides consisiting of L- and D-amino acids form ion channels in artificial and biological membranes (Carpaneto et al. 2002; Szabó et al. 2004; Szabó et al. 2002; Agner et al. 2000; Dalla Serra et al. 1999; Hutchison and Gross 1997). These pore-forming phytotoxic, cyclic lipodepsipeptides include syringopeptin22A1, syringopeptin25A, syringomycin E, syringolin A, and syringotoxin, all synthesized by the phytopathogen, Pseudomonas syringae (Amrein et al. 2004; Bender et al. 1999). These toxic agents exhibit fungicidal, antibacterial and hemolytic activities (Szabó et al. 2002; Buber et al. 2002; Fogliano et al. 2002). They are all made by multimodular synthetases, and their biosynthesis, export and regulation have been studied (Kang and Gross 2005; Scholz-Schroeder et al. 2003). Related toxins include pseudophomins, fuscopeptins, corpeptins arthrofactin and ramoplanin (Balibar et al. 2005; Coraiola et al. 2008). Another cyclic lipodepsipeptide is phaeofungin, produced by the fungus, Phaeosphaeria sp. It consists of seven D- and L-amino acids and a β,γ-dihydroxy-γ-methylhexadecanoic acid arranged in a 25-membered cyclic depsipeptide (Singh et al. 2013). A related fungal lipodepsipeptide is phomafungin from Phoma sp. Many Pseudomonads, other bacteria and fungi synthesize these toxic agents (Scaloni et al. 2004; Miao et al. 2006). Syringopeptin 25A (SP25A) inserts into artificial membranes in two starges, the first stage is ascribed to large channels resulting from the aggregation of small ones, while the second more negative stage is associated with the small channels resulting from the disaggregation of the large ones (Becucci et al. 2016).