All creatures need metals for their enzymes to function, yet even minute amounts can be toxic to cells. The discovery, reported in the current issue of Science , may help researchers probe the molecular causes of conditions, such as Lou Gehrig's disease , that are thought to be the result of metal metabolism gone awry.
Scientists have a pretty good idea how cells handle excess amounts of metals.
When levels build up, certain proteins bind the metals into clusters to prevent them from poisoning the cell, and others expel these compounds from the cell. But how cells deal with the tiny quantities their enzymes need is more mysterious. Valerie Culotta of Johns Hopkins University had come across an intriguing protein made by a yeast gene called Atx1 . Culotta and Tom O'Halloran, an inorganic chemist at Northwestern University, suspected that Atx1 may be trafficking in metals because it resembled a protein that rids cells of mercury. The Atx1 protein has a strong liking for copper, binding to it even when outnumbered by other organic molecules known to be attracted to the metal.