Sandbox Reserved 764: Difference between revisions

The three-dimensional structure of EPSP synthase in ''Escherichia coli'' was determined using X-ray crystallography. The enzyme has two distinct domains, each of which have a radius of approximately 25 Angstroms <ref>PMID:11607190</ref>. The two domains are joined together by two crossover chain segments with both the amino and carboxyl terminus of the polypeptide chain located in the C-terminal domain. The domains are formed by protein folding subunits consisting of the following <scene name='56/564040/Epsp_synthase/2'>secondary structures</scene>: two parallel helices and  four beta sheets <ref>PMID:11607190</ref>. Each domain is formed from three of these subunits, forming the threefold axis of symmetry shown below in Figure 3. Three alpha helices are positioned around the axis of each domain to form its core. The domain surfaces consist of three beta-sheets and three parallel helices that are all solvent accessible <ref>PMID:11607190</ref>. The beta sheets can be found in both the parallel and anti-parallel positions. The alpha helices are positioned in a parallel fashion that establishes equivalent chain polarities throughout the enzyme. It is believed that the helix dipole establishes optimal interaction between the enzyme and charged phosphate groups of the substrates <ref> W. G. J. Hol, P. T. van Duijnen & H. J. C. The [alpha]-helix dipole and the properties of proteins: Nature 273, 443-446 (8 June 1978).[http://dx.doi.org/10.1038/273443a0 DOI:10.1038/273443a0</ref>. Studies suggest that these helical dipole efffects create a cationic well that draws the anionic substrates into the active site located in the interdomain cleft.