A novel membrane glycoprotein of Escherichia coli

A novel glycoprotein (Gp45) has been isolated and purified from Escherichia coli. To our knowledge, Gp45 is the third glycoprotein isolated from E. coli membrane and it is the second in the non-pathogenic strain of the organism. For the isolation of Gp45, cell extract or membrane fraction was treated with sodium deoxycholate for 4 h and precipitated with trichloroacetic acid (TCA). The supernatant fraction of TCA containing the Gp45 was further purified on DEAE-Sephadex A-25. SDS-PAGE showed a single band at 45 kDa position that stained with periodic-Schiff reagent. It contained 60% carbohydrate and 40% protein content. The monosaccharide composition also substantiated the characteristics of the glycoprotein. The E. coli grown in presence of (14)C-glucosamine further confirmed the localization and biosynthesis of this glycoprotein on the membrane during the growth phase. Bacitracin, a general inhibitor of the glycosylation, inhibited its biosynthesis.