Memnopeptide A, a Novel Terpene Peptide from Memnoniella with an Activating Effect on SERCA2

The terpene peptide memnopeptide A (1), C76H108N16O18S, MW 1564, was isolated from a culture of the fungus Memnoniella echinata FH 2272 on casein peptone. The structure of the novel compound was elucidated with the aid of 2D NMR experiments and from amino acid analysis and mass spectrometric sequencing of the peptide. The compound consists of a known phenylspirodrimane subunit linked to the decapeptide Met-His-Gln-Pro-His-Gln-Pro-Leu-Pro-Pro. This proline-rich peptide is a subsequence of β-casein. From the observed absence in the literature of any other highly significant sequence homologues, memnopeptide A can be assumed to arise from metabolic products of the fungus with direct incorporation of constituents of the nutrient medium. The formation of memnopeptide A suggests this may be a mechanism for storage of amines by the fungus. Memnopeptide A has weak antibacterial activity against Gram-positive bacteria and effects half-maximal activation of sarco(endo)plasmic reticulum Ca2+ ATPase (SERCA2) at a concentration of 12.5 μm.