Determination of the solution conformation of dephospho coenzyme A by nuclear-magnetic-resonance spectroscopy with lanthanide probes. A method for analysis when more than one complex species is present

The aqueous solution conformation of the 1 : 1 complex of dephospho CoA bound to a lanthanide ion has been determined by examination of the dipolar shift and induced relaxation at pH 6.4. The experimental data are shown to arise from the presence of both 1 : 1 and 1 : 2 metal : ligand complexes and a graphical method is described to divide the experimental data into information corresponding to each of the two species. The formation constants are also derived. For the 1 : 1 complex the ribose is found in a 2E conformation with the adenine base predominantly anti. A small contribution from a syn conformation is evident. The pantoinic acid fragment of the chain is folded back towards the pyrophosphate while the remainder of the chain is extended.