Novel fluorescent labelled affinity probes for diadenosine-5′,5 -P1,P4-tetraphosphate (Ap4A)-binding studies

Tandem synthetic–biosynthetic procedures were used to prepare two novel fluorescent labelled affinity probes for diadenosine-5′,5 -P1,P4-tetraphosphate (Ap4A)-binding studies. These compounds (dial-mant-Ap4A and azido-mant-Ap4A) are shown to clearly distinguish known Ap4A-binding proteins from Escherichia coli (LysU and GroEL) and a variety of other control proteins. Successful labelling of chaperonin GroEL appears to be allosteric with respect to the well-characterized adenosine 5′-triphosphate (ATP)-binding site, suggesting that GroEL possesses a distinct Ap4A-binding site.