title: Crystallization and preliminary crystallographic analysis of cysteine synthase from Entamoeba histolytica.
abstract: Entamoeba histolytica, the causative agent of human amoebiasis, is essentially anaerobic, requiring a small amount of oxygen for growth. It cannot tolerate the higher concentration of oxygen present in human tissues or blood. However, during tissue invasion it is exposed to a higher level of oxygen, leading to oxygen stress. Cysteine, which is a vital thiol in E. histolytica, plays an essential role in its oxygen-defence mechanisms. The major route of cysteine biosynthesis in this parasite is the condensation of O-acetylserine with sulfide by the de novo cysteine-biosynthetic pathway, which involves cysteine synthase (EhCS) as a key enzyme. In this study, EhCS was cloned, expressed in Escherichia coli and purified by affinity and size-exclusion chromatography. The purified protein was crystallized in space group P4(1) with two molecules per asymmetric unit and a complete data set was collected to a resolution of 1.86 A. A molecular-replacement solution was obtained using the Salmonella typhimurium O-acetylserine sulfhydrylase structure as a probe and had a correlation coefficient of 37.7% and an R factor of 48.8%.
authors.affiliation: School of Life Sciences, Jawaharlal Nehru University, New Delhi, India.
authors.forename: Chinthalapudi
authors.initials: C
authors.lastname: Krishna
authors.forename: Ruchi
authors.initials: R
authors.lastname: Jain
authors.forename: Tara
authors.initials: T
authors.lastname: Kashav
authors.forename: Dinakar
authors.initials: D
authors.lastname: Wadhwa
authors.forename: Neelima
authors.initials: N
authors.lastname: Alam
authors.forename: S
authors.initials: S
authors.lastname: Gourinath
mesh_terms: D000818:Animals; D003460:Crystallization; D018360:Crystallography, X-Ray; D003547:Cysteine Synthase / Q000737:chemistry* / Q000302:isolation & purification; D004748:Entamoeba histolytica / Q000201:enzymology*
chemical_list: D003547:Cysteine Synthase