Characterisation of stress protein LysU. Enzymic synthesis of diadenosine 5′,5‴-P ¹ ,P ⁴ -tetraphosphate (Ap ₄ A) analogues by LysU

The stress protein LysU (lysyl tRNA synthetase) has been purified from a recombinant strain of Escherichia coli expressing the plasmid pXLys5, and kinetically characterised. Preparative syntheses of analogues of the biologically important molecule diadenosine 5′,5‴-P1,P4-tetraphosphate (Ap4A) are then achieved in good yield by enzyme catalysis, using purified LysU.