The role of zinc in cell division and protein synthesis has been known for a long time, but recently
a new class of zinc-dependent protein molecules (zinc metalloproteins) has been identified in DNA
replication and transcription, thus regulating gene expression (10,11)
. Zinc is required for binding
of specific genes with tetrahedral bonds that result in transcription. By this means the polypeptide
chain forms a loop of usually 11 to 13 amino acid residues, which bind the specific DNA sequences.
Zinc is therefore directly involved in the translation step of gene expression of DNA elements in
these DNA-binding metalloproteins.
Amino acids accumulate in zinc-deficient plants as protein content decreases (54)
. Protein synthesis
resumes when zinc is resupplied because zinc is a structural component of the ribosomes and
responsible for their structural integrity. Ribosomes disintegrate in the absence of zinc, but reconstitution
reoccurs with the resupply of zinc.