Stereospecific 1H and 13C NMR Assignments of Crotonyl CoA and Hexadienoyl CoA: Conformational Analysis and Comparison with Protein−CoA Complexes

Stereospecific 1 H and 13 C resonance assignments of hexadienoyl-CoA and crotonyl-CoA have been determined. The two diastereotopic methyl groups at the C2‘‘ carbon were assigned via transferred nuclear Overhauser effect experiments on the complex of hexadienoyl-CoA with the enzyme enoyl-CoA hydratase. The two diastereotopic 1‘‘ protons were assigned using heteronuclear multiple-bond correlation experiments in conjunction with rotating frame nuclear Overhauser spectroscopy. This represents the first set of complete stereospecific assignments for any CoA derivative. The assignments allow a detailed quantitative conformational analysis of the uncomplexed form of the molecule. In particular, the relative population of the various rotamers about the C1‘‘−C2‘‘ and the C2‘‘−C3‘‘ bonds have been determined. The database of protein-bound CoA structures has been surveyed and used to compare the structure(s) of CoA in protein−CoA complexes with the conformational preferences of free CoA.