A study of apo- and holo-forms of horse liver alcohol dehydrogenase in solution by diffuse X-ray scattering

Apo‐ and holo‐forms of horse liver alcohol dehydrogenase (LADH) in solution were studied by diffuse x‐ray scattering. Experimental scattering curves for apo‐ and holo‐forms coincide both with the curves calculated from the crystal structures of apo‐ and holo‐enzymes, and with each other. Thus the “sliding” of catalytical domains in LADH upon substrate binding, which has been shown by x‐ray analysis, cannot be detected by diffuse x‐ray scattering. Sensitivity of the scattering curves to the domain displacements of sliding and “locking” types has been investigated. It has been shown that the scattering curves of LADH are rather sensitive to the domain “unlocking.” However, these curves change only slightly upon sliding of domains, including the sliding of domains observed in LADH by x‐ray analysis.