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Infect. Immun., 12 1996, 5144-5150, Vol 64, No. 12
A Wada, T Hirayama, H Kitaura, J Fujisawa, M Hasegawa, Y Hidaka and Y Shimonishi
Guanylyl cyclase C (STaR), a receptor protein for heat-stable enterotoxin
(STa) elaborated by Escherichia coli, is associated with and spans the
plasma membrane of mammalian intestinal cells. The extracellular domain
functions in the binding of STa and the association of each domain to an
oligomeric form. Two amino acid residues, Arg-136 and Asp-347, were
identified as the residues binding to STa in the extracellular domain of
pig STaR by site-directed mutagenesis and analysis of expression on 293T
cells. Replacement of these residues by other amino acid residues resulted
in the loss of binding of pig STaR to STa, and as a result, STa-induced
guanylyl cyclase activity was eliminated. Furthermore, mutation in a region
(from Asp-347 to Val-401) which is close to the transmembrane domain caused
a significant reduction in both STa-binding activity and guanylyl cyclase
catalytic activity. These results suggest that the region adjacent to the
transmembrane domain plays an important role in facilitating a favorable
conformation of STaR for STa binding.
Copyright © 1996, American Society for Microbiology
Identification of ligand recognition sites in heat-stable enterotoxin receptor, membrane-associated guanylyl cyclase C by site-directed mutational analysis
Institute for Protein Research, Osaka University, Suita, Japan.
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