Identification and Characterization of<i>gshA</i>, a Gene Encoding the Glutamate-Cysteine Ligase in the Halophilic Archaeon<i>Haloferax volcanii</i>

Abstract

Halophilic archaea were found to contain in their cytoplasm millimolar concentrations of gamma-glutamylcysteine (gamma GC) instead of glutathione. Previous analysis of the genome sequence of the archaeon Halobacterium sp. strain NRC-1 has indicated the presence of a sequence homologous to sequences known to encode the glutamate-cysteine ligase GshA. We report here the identification of the gshA gene in the extremely halophilic archaeon Haloferax volcanii and show that H. volcanii gshA directs in vivo the synthesis and accumulation of gamma GC. We also show that the H. volcanii gene when expressed in an Escherichia coli strain lacking functional GshA is able to restore synthesis of glutathione.