Inelastic neutron scattering analysis of hexokinase dynamics and its modification on binding of glucose

Abstract

The dynamical behaviour of proteins and its significance to protein function has become the subject of considerable experimental and theoretical investigation^1,2. The existence of atomic motion about mean positions has been well established by the temperature dependence of X-ray diffraction³ and it has long been recognized that considerable internal mobility is required in proteins to account for hydrogen exchange measurements⁴. However, only limited experimental information, mainly obtained by optical methods⁵, is available on the frequencies associated with these fluctuations. Inelastic neutron scattering is a technique capable of yielding dynamical information about a system over a wide frequency range^6,7. Recent advances in neutron spectrometers⁸ and in the theoretical understanding of the dynamics of biological macromolecules have now made it both feasible and desirable to exploit this technique in the field of biophysics. To demonstrate the potential of the method, we report here data on the frequency distribution in solution of the enzyme hexokinase and its modification brought about on binding of its substrate glucose. The results lend support to the view that ligation induces a stiffening of the enzyme structure.