Experimental Evidence for a Metal‐Related Function of a Cyanobactin

Abstract

ABSTRACT The cyanobacterium Prochloron didemni produces macrocyclic octapeptides with thiazole and oxazoline heterocycles, known as patellamides. An interesting observation is that Cu 2+ binding to the patellamides is likely to be related to their biological function. First, we show that Cu 2 +  injection into Lissoclinum patella increases patG gene expression and patellamide levels in the ascidians. Second, x‐ray absorption spectroscopy shows that biological extracts of specimen from the Great Barrier Reef match structurally synthetic carbonato‐bridged dicopper(II)‐patellamide complexes. Third, patellamides exhibit very high membrane permeability (PAMPA, Caco‐2). Combined with intracellular pH data, patellamide‐Cu 2 + bioactivity in algae, and the absence of many of the typical CO 2 uptake mechanisms in Prochloron , we propose that patellamides facilitate carbonate transport from the ascidians to the cyanobacteria. This provides unprecedented evidence for a link between cyanobactin metal binding and their production and function, suggesting possible novel metal‐related roles for marine cyclic peptides.