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Medical AI Inquiry: You was designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.  Labels: OBJECTIVE, METHODS, RESULTS. Meshes: Amino Acid Sequence, Animals, Antibodies, Monoclonal, Bacterial Proteins, CHO Cells, Chloride Channels, Colon, Cricetinae, Cyclic AMP, Gene Expression Regulation, Enzymologic, Intestinal Mucosa, Molecular Sequence Data, Necturus, Oocytes, Sucrase-Isomaltase Complex, Transfection, Xenopus laevis, alpha-Glucosidases.
user
Is sucrase-isomaltase an adenosine 3',5'-cyclic monophosphate-dependent epithelial chloride channel? Context: We previously isolated a monoclonal antibody against a Necturus gallbladder epitope that blocks native adenosine 3',5'-cyclic monophosphate (cAMP)-dependent chloride channels in intestine, gallbladder, urinary bladder, and airway epithelia in various animals. Using this antibody, we purified a 200-kilodalton protein that, when reconstituted in lipid bilayers, forms 9-pS chloride channels that are blocked by the antibody. Amino acid sequencing of the purified protein showed strong homology to rabbit sucrase-isomaltase, an abundant intestinal enzyme. Western blot analysis of the in vitro-translated sucrase-isomaltase was indistinguishable from that of the protein used in the lipid bilayer studies. Expression of this protein in Chinese hamster ovary cells and in Xenopus laevis oocytes yielded cAMP-dependent chloride currents that in the latter system were blocked by the antibody.
assistant
Because the monoclonal antibody blocks cAMP-dependent currents in epithelia as well as those produced both by the reconstituted and by the heterologously expressed protein, sucrase-isomaltase is a cAMP-dependent epithelial chloride channel. Thus an enzyme that can also function as an ion channel has been described for the first time. Final Decision: yes