CLONING AND SEQUENCING OF THE GENE ENCODING THE CELL-SURFACE GLYCOPROTEIN OF HALOARCULA-JAPONICA STRAIN TR-1

The triangular disk-shaped halophilic archaeon Haloarcula japonica str ain TR-1 has a glycoprotein on its cell surface. The complete gene enc oding the cell surface glycoprotein (CSG) was cloned and sequenced. Th e gene has an open reading frame of 2586bp, and a potential archaeal p romoter sequence approximately 150bp upstream of the ATG initiation co don. The mature CSG is composed of 828 amino acids and is preceded by a signal sequence of 34 amino acid residues. A hydropathy analysis sho wed a hydrophobic stretch at the C-terminus, that probably serves as a transmembrane domain. The amino acid sequence of the Ha. japonica CSG showed 52.1% and 43.2% identities to those from the Halobacterium hal obium and Haloferax volcanii CSGs, respectively. Five potential N-glyc osylation sites were found in the mature Ha. japonica CSG, sites that were distinctly different from those in Hb. halobium and Hf. volcanii. The Ha. japonica CSG gene was expressed in Escherichia coli.