Immunogen sequence: MGCRAASGLL PGVAVVLLLL LQSTQSVYIQ YQGFRVQLES MKKLSDLEAQ WAPSPRLQAQ SLLPAVCHHP ALPQDLQPVC ASQEASSIFK TLRTIANDDC; Positive Samples: Mouse small intestine. Endogenous activator of intestinal guanylate cyclase. It stimulates this enzyme th