SAN DIEGO, Nov. 7 (UPI) -- U.S. researchers say trace-metal usage by modern organisms probably derives from major changes in ocean chemistry occurring over geological time scales.
The study sought to verify the theory that the rise in atmospheric oxygen some 2.3 billion years ago, and attendant shifts in ocean chemistry, led to changes in types of metals used with protein structures. Such changes are hypothesized to have led to the diversification and increased complexity of life.
Scientists Chris Dupont, Song Yang, Brian Palenik and Philip Bourne from the San Diego Supercomputer Center, Scripps Institution of Oceanography and the University of California-San Diego analyzed the metal-binding characteristics of all protein structures found in all kingdoms of life.
The group found the three superkingdoms of life -- Archaea, Bacteria and Eukarya -- all use metals differently. The differences reflect the availability of such metals in the ocean as the respective superkingdoms evolved.
"These conserved trends are proteomic imprints of changes in trace-metal bioavailability in the ancient ocean that highlight a major evolutionary shift in biological trace-metal usage," the researchers said.
The study appears in this week's edition of the Proceedings of the National Academy of Sciences.