Abstract

Nuclear magnetic resonance spectra of acylphosphatase were searched for signs of β-structure, i.e. characteristic nuclear Overhauser enhancement patterns displayed in the two-dimensional spectra, typical chemical shifts, coupling constants and slow ²H---H exchange. The results provided identification of the main-chain resonances of amino acid residues involved in the β-structure. The full sequential assignment of this region was gained by identification of some amino acid spin systems and their alignment with the primary sequence. The assignment of the side-chains was virtually completed subsequently and a list produced of nuclear magnetic resonance (n.m.r.) constraints derived from the spectra. The β-structure consists of a β-sheet with four antiparallel chains, one attached parallel chain, three tight turns and a β-bulge. The conformation of the β-sheet was determined by distance geometry calculation using the n.m.r. constraints (174 intraresidual, 107 sequential and 226 long-range distances, 32 torsion angles, Φ, and 28 hydrogen bonds) as input. Observation of some interactions between the sheet and previously identified α-helical regions made it possible to give an outline of the three-dimensional structure of the enzyme.

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^† Present address: Marrell Dow Research Institute, 16 rue d'Ankura, Strasbourg, 67084 France.