Zinc through the Three Domains of Life

Zinc is one of the metal ions essential for life, as it is required for the proper functioning of a large
number of proteins. Despite its importance, the annotation of zinc-binding proteins in gene banks or
protein domain databases still has significant room for improvement. In the present work, we compiled
a list of known zinc-binding protein domains and of known zinc-binding sequence motifs (zinc-binding
patterns), and then used them jointly to analyze the proteome of 57 different organisms to obtain an
overview of zinc usage by archaeal, bacterial, and eukaryotic organisms. Zinc-binding proteins are an
abundant fraction of these proteomes, ranging between 4% and 10%. The number of zinc-binding
proteins correlates linearly with the total number of proteins encoded by the genome of an organism,
but the proportionality constant of Eukaryota (8.8%) is significantly higher than that observed in Bacteria
and Archaea (from 5% to 6%). Most of this enrichment is due to the larger portfolio of regulatory proteins
in Eukaryota.
Keywords: Zinc • metalloproteins • gene expression • zinc fingers