Low resolution structure of adenylate kinase

A low resolution model of adenylate kinase has been derived from a 6 Å electron density map. The molecular shape can be described approximately as an oblate ellipsoid with dimensions 40 Å × 40 Å × 30 Å. The molecule is composed of two globular units separated by a 10 Å deep cleft. In contrast to the bigger unit, the smaller globule appears to contain a high amount of α-helical structure. The location of the active centre is discussed. The crystals used for X-ray diffraction analysis belong to one of the enantiomorphic trigonal space groups P3 121 or P3 221, with one molecule in the asymmetric unit. The phase determination was based on four isomorphous heavy atom derivatives. Frequent transitions between different crystal forms complicate the analysis.