Purification and Characterization of Putative Glutathionylspermidine synthetase, YgiC from Escherichia coli

Abstract

Glutathione (γ-Glu-Cys-Gly) is a tripeptide-, and a primary thiol found in most organisms. It regulates intracellular thiol levels and maintains redox balance. In Escherichia coli glutathione reacts with polyamine spermidine (N-(3-amino) propyl-1, 4-diaminobutane) to form a conjugate glutathionylspermidine (G-Sp). This reaction is catalyzed by an ATP-dependent bifunctional enzyme glutathionylspermidine synthetase/amidase. Genes ygiC and yjfC in E. coli genome are associated with putative glutathionylspermidine synthetase activity. The purpose of our research was to characterize the glutathionylspermidine synthetase homologue, YgiC (45 kD). Overexpression and purification of YgiC protein were attempted in order to perform the activity studies. Several different growth conditions were utilized to achieve the expression of YgiC protein in BL21(DE3) E. coli cells. Chromatographic techniques namely ion exchange, hydrophobic interaction and gel filtration chromatography were employed for protein purification.