Year: 2002
Type: conference-abstract
Abstract: E. coli porphobilinogen synthase(PBGS) is an octameric enzyme that catalyzes the asymmetric condensation of two molecules of 5-aminolevulinic acid(ALA) to yield porphobilinogen, a precursor to pyrroles.Crystals of PBGS grown from a solution containing ALA and 2.2 M MgSO4 at pH = 8 diffract to 2.4 Å in space group P42212 with a = 130.3,c = 143.4Å.The addition of heavy metal ions causes the crystals to diffract to no better than 3 Å and to transform to I422.For the PBGS:ALA crystals, the reflections which make the cell primitive(h + k + l = odd) are weak relative to the (h + k + l = 2n) reflections.Molecular replacement for the primitive case gives two molecules related by a translation vector (1/2,1/2,1/2).Ignoring the (h + k + l = odd) data yields either I4 or P422 as the spacegroup.The structure has been refined in all three spacegroups with the worst refinement statistics going to P42212 and the best to I4 with R = 0.175 and Rfree = 0.219.There is no evidence of twinning so 'Which is the correct answer?'.P42212 is certainly the correct answer even though the statistics are better for the other choices.The final result is still to come.This work is supported by grant CA-10925 from the National Institutes of Health and by an
Authors: M. S. Chapman, M. Yousef, S. A. Clark, P. Pruett, A. Azzi, J. Gattis, F. Fabiola, T. Somasundaram, W. R. Ellington
Language: English
Subfield: Materials Chemistry
Field: Materials Science
Domain: Physical Sciences
Open Access status: bronze
Funder: National Institutes of Health
OpenAlex ID: W1997238375