In the presence of purified Escherichia coli lysyl-tRNA synthetase [L-lysine:tRNALys ligase (AMP-forming) EC 6.1.1.6], L-lysine, and ATP, addition of the nucleotide ppGpp results in formation of a unique product-A(5')ppp(5') Gpp. The same compound is also formed very rapidly in a cell-free protein-synthesizing system when ppGpp is added. The possible significance of this reaction in the rapid turnover of ppGpp and as a more general mechanism by which an AMP residue is activated and introduced onto a 5'-diphosphorylated species, including the 5'-end of an RNA, is further discussed.
Adenine Nucleotides Adenosine Triphosphate