ABSTRACT
At present, above 5900 genomes of living organisms have been
completely sequenced and stored as text-based data files through
the Internet-based database systems. Most database systems were
made freely available to the public through the World Wide Web-
based systems, such as the National Center for Biotechnology In-
formation (NCBI) Entrez,1 the Kyoto Encyclopedia of Genes and
Genomes (KEGG),2 and the Genomes OnLine Database (GOLD).3 It
is estimated that more than one third of all known proteins are
metalloproteins, which require metals to maintain their structures
and functions in living organisms.4 Obviously, there is not enough
experimental evidence to elucidate metal-selection mechanisms of
the complete set of metalloproteins encoded by genomes of living
organisms. Based on Irving-Williams series of relative stabilities of
complexes formed by metal ions (Ca2+ < Mg2+ < Mn2+ < Fe2+ < Co2+ < Ni2+ < Cu2+ > Zn2+),5 metalloproteins would bind most strongly to divalent (cupric) copper, and to a lower strength to other
metal ions. To maintain life systems, however, metalloproteins must
selectively bind to specific metal ions required for their function. Re-
cently, it is proposed that metal-binding selectivity of metallopro-
teins is determined by spatiotemporal folding of the proteins in the
cells, and not only by the basis of the nature, number, and geometric
arrangement of the binding residues, or the size and charge of the
metal-binding pocket.6
