Fluoride, beryllium and ADP combine as a ternary complex in aqueous solution as revealed by a multinuclear NMR study

Different kinds of nucleotide binding enzymes are sensitive to fluoroberyllate complexes (BeFx) and fluoroaluminate complexes (AlFy). It has been hypothesized that the effects of these fluorometals are related to the generation at a nucleotide binding site of a pseudo nucleoside triphosphate, consisting of a fluorometal moiety bound to the beta phosphate group of a molecule of nucleoside diphosphate (Bigay et al. 1985; Lunardi et al. 1985). In order to establish whether ternary complexes comprising ADP, beryllium and fluoride can exist in slightly alkaline solution in the absence of enzyme, we have carried out a multinuclear (31P, 9Be and 19F) NMR study. In preliminary experiments, pyrophosphate (PPi) was substituted for ADP and taken as a simpler analog of nucleoside diphosphate. In the absence of fluoride, three types of PPi-Be complexes were generated: two of these were bidentate chelates with either one or two pyrophosphate molecules bound per beryllium; the third one was a monodentate complex. It is probable that the same types of combination exist between the polyphosphate chain of ADP and Be. In the presence of fluoride, both ADP and PPi combined with beryllium to form ternary complexes. These complexes consisted of monofluoroberyllate(-BeF) or difluoroberyllate(-BeF2) bound to the two phosphates of one molecule of ADP or PPi as a bidentate chelate. We failed to observe the formation of complexes between ADP and trifluoroberyllate(-BeF3). The relevance of this study to the biological effects of fluoride and beryllium on various enzymic reactions is discussed.