Int J Biochem Mol Biol 2012;3(3):302-312
Original Article
Comparison of the functions of glutathionylspermidine synthetase/amidase from E. coli
and its predicted homologues YgiC and YjfC
Li Sui, John C Warren, Janelle PN Russell, Nina V Stourman
Center for Applied Chemical Biology, Youngstown State University, One University Plaza, Youngstown, OH, 44555, USA; Department of
Chemistry, Youngstown State University, One University Plaza, Youngstown, OH, 44555, USA
Received July 31, 2012; Accepted September 18, 2012; Epub September 25, 2012; Published September 30, 2012
Abstract: Protein function prediction is very important in establishing the roles of various proteins in bacteria; however, some proteins in the E.
coli genome have their function assigned based on low percent sequence homology that does not provide reliable assignments. We have
made an attempt to verify the prediction that E. coli genes ygiC and yjfC encode proteins with the same function as glutathionylspermidine
synthetase/amidase (GspSA). GspSA is a bifunctional enzyme that catalyzes the ATP-dependent formation and hydrolysis of
glutathionylspermidine (G-Sp), a conjugate of glutathione (GSH) and spermidine. YgiC and YjfC proteins show 51% identity between
themselves and 28% identity to the synthetase domain of the GspSA enzyme. YgiC and YjfC proteins were expressed and purified, and the
properties of GspSA, YgiC, and YjfC were compared. In contrast to GspSA, proteins YgiC and YjfC did not bind to G-Sp immobilized on the
affinity matrix. We demonstrated that all three proteins (GspSA, YgiC and YjfC) catalyze the hydrolysis of ATP; however, YgiC and YjfC cannot
synthesize G-Sp, GSH, or GSH intermediates. gsp, ygiC, and yjfC genes were eliminated from the E. coli genome to test the ability of mutant
strains to synthesize G-Sp conjugate. E. coli cells deficient in GspSA do not produce G-Sp while synthesis of the conjugate is not affected in
ΔygiC and ΔyjfC mutants. All together our results indicate that YgiC and YjfC are not glutathionylspermidine synthetases as predicted from the
amino acid sequence analysis. (IJBMB1207004).
Keywords: Glutathione, glutathionylspermidine, glutathionylspermidine synthetase/amidase, ATPase, ATP-grasp domain
Address all correspondence to:
Dr. Lijun Jia
Department of Immunology
Shanghai Medical College
Fudan University Shanghai 200032, China.
Tel: 86-21-54237751
E-mail: jialijun2002@yahoo.com.cn
Original Article
Comparison of the functions of glutathionylspermidine synthetase/amidase from E. coli
and its predicted homologues YgiC and YjfC
Li Sui, John C Warren, Janelle PN Russell, Nina V Stourman
Center for Applied Chemical Biology, Youngstown State University, One University Plaza, Youngstown, OH, 44555, USA; Department of
Chemistry, Youngstown State University, One University Plaza, Youngstown, OH, 44555, USA
Received July 31, 2012; Accepted September 18, 2012; Epub September 25, 2012; Published September 30, 2012
Abstract: Protein function prediction is very important in establishing the roles of various proteins in bacteria; however, some proteins in the E.
coli genome have their function assigned based on low percent sequence homology that does not provide reliable assignments. We have
made an attempt to verify the prediction that E. coli genes ygiC and yjfC encode proteins with the same function as glutathionylspermidine
synthetase/amidase (GspSA). GspSA is a bifunctional enzyme that catalyzes the ATP-dependent formation and hydrolysis of
glutathionylspermidine (G-Sp), a conjugate of glutathione (GSH) and spermidine. YgiC and YjfC proteins show 51% identity between
themselves and 28% identity to the synthetase domain of the GspSA enzyme. YgiC and YjfC proteins were expressed and purified, and the
properties of GspSA, YgiC, and YjfC were compared. In contrast to GspSA, proteins YgiC and YjfC did not bind to G-Sp immobilized on the
affinity matrix. We demonstrated that all three proteins (GspSA, YgiC and YjfC) catalyze the hydrolysis of ATP; however, YgiC and YjfC cannot
synthesize G-Sp, GSH, or GSH intermediates. gsp, ygiC, and yjfC genes were eliminated from the E. coli genome to test the ability of mutant
strains to synthesize G-Sp conjugate. E. coli cells deficient in GspSA do not produce G-Sp while synthesis of the conjugate is not affected in
ΔygiC and ΔyjfC mutants. All together our results indicate that YgiC and YjfC are not glutathionylspermidine synthetases as predicted from the
amino acid sequence analysis. (IJBMB1207004).
Keywords: Glutathione, glutathionylspermidine, glutathionylspermidine synthetase/amidase, ATPase, ATP-grasp domain
Address all correspondence to:
Dr. Lijun Jia
Department of Immunology
Shanghai Medical College
Fudan University Shanghai 200032, China.
Tel: 86-21-54237751
E-mail: jialijun2002@yahoo.com.cn
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