Identification of a new sialic acid-binding protein in Helicobacter pylori

A novel sialic acid-specific lectin has been isolated from Helicobacter pylori lysate using fetuin–agarose affinity chromatography followed by cleavage of the α(2,3) and α(2,6) linkages of sialic acids using neuraminidase. The protein had a molecular weight of 17.5 kDa on sodium dodecyl sulfate (SDS)–polyacrylamide gel electrophoresis (PAGE) and was identified by matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF) mass spectrometry to be protein of unknown function with gene number HP0721. Recombinant HP0721 was shown to bind to fetuin–agarose and sialic acid-containing glycosphingolipids on thin-layer plates suggesting this protein may represent another sialic acid-specific adhesin of H. pylori. A H. pylori mutant defective for HP0721 was generated and its ability to bind to human AGS cells assayed.