SDS-PAGE analysis of purified urease B and Western blot analysis of urease B reactivity with patient serum. (A) Bacteria expressing GST-urease B were lysed by sonication, and the supernatant was applied to a Glutathione Sepharose 4B column. Purified urease B was analysed on a 10% SDS-PAGE. 1: purified urease B; 2: protein marker. (B and C) The gels were transferred to nitrocellulose membranes and probed with diluted human sera (1:50) from a normal donor or an H. pylori-infected patient. Detection was performed with a goat anti-human antibody linked to HRP (1:10,000), followed by staining with 3-amino-9-ethylcarbozole. 1: GST; 2: urease B; 3: protein marker.