The role of zinc in 5',5'-diadenosine tetraphosphate production by aminoacyl-transfer RNA synthetases.

Aminoacyl-tRNA synthetases are capable of converting 5'-ATP into 5',5'-diadenosine tetraphosphate. The reaction reflects the reversal of enzyme-bound aminoacyl-adenylate by ATP instead of PPi. In the case of a few prokaryotic as well as eukaryotic aminoacyl-tRNA synthetases, the initial rate of diadenosine tetraphosphate synthesis can be greatly enhanced upon adding small amounts of zinc. This observation enables us to establish a relationship between diadenosine tetraphosphate, a nucleotide possibly involved in controlling cell proliferation, and a metallic cofactor, which is believed to play a role in tumour growth.