Copper-handling by Polaris and the metallation-status of ETR1

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The Lindsey laboratory has (over several years) discovered a role for a short polypeptide (POLARIS) in the control of plant development and more specifically in regulatory circuits that are triggered by ethylene. They have (amongst other observations) established that the POLARIS peptide co-localises with the ethylene receptor ETR1 in intracellular membraneous compartments. Importantly, ETR1 is known to need to coordinate copper in order to form a vital cation-pi interaction with its gaseous signal molecule. Because POLARIS has candidate copper-ligands, we recently tested whether or not it may also coordinate copper and have (to date) already established that it can indeed form a complex with cuprous ions. Coincidentally, the Lindsey laboratory has also observed that copper or copper-chelation (by bathocuproinedisulphonic acid) can modify, and in some cases reverse, the phenotypes associated with POLARIS mutants. This has created an exciting opportunity to understand how ethylene signalling may be controlled via metallation of ETR1 with copper. Moreover, from the copper-transporting Menkes and Wilsons ATPases in humans, the RAN1 and CCC2 transporters of plants and yeast, to the CopA like copper-ATPases of bacteria such as Legionella, it remains a mystery how copper is managed after transport into intracellular membraneous compartments (or the periplasm of bacteria) to enable delivery to bona fide, awaiting cupro-proteins, in these locations: The POLARIS-ETR1 copper-'circuitry' could become a universal paradigm.