Some Ins and Outs of Nickel Trafficking

April 25, 2014

Mike Maroney

Metal ion homeostasis is essential for all living organisms, and defects in the metal-trafficking
proteins involved lead to a number of human diseases. A viable metal-trafficking system must be
able to distinguish one metal from another, and knowledge of how this is achieved is lacking. The
nickel trafficking system is attractive for study from the standpoint that the number of targets
(enzymes dependent on nickel) is small, and thus the traffic pattern is simple, though it features
the proteins that perform the functions that are essential to all transition metal trafficking systems:
controlling import and export (metallotransporters), targeting the delivery of metals to specific
enzymes (metallochaperones) or involvement in metallocenter assembly (accessory proteins),
and regulating the expression of the other proteins in response to metal ion availability
(metalloregulators). In addition, since mammals utilize no known nickel-dependent enzymes,
understanding of nickel trafficking may offer a useful antibiotic strategy. Studies aimed at
determining how various proteins involved in nickel trafficking distinguish nickel from other metals
will be described using examples from E. coli and Helicobacter pylori.