Intestinal brush border membrane Na+/glucose cotransporter functions in situ as a homotetramer

Journal Article · Thu Feb 01 04:00:00 EST 1990 · Proceedings of the National Academy of Sciences of the United States of America; (USA)

DOI:https://doi.org/10.1073/pnas.87.4.1456· OSTI ID:7025507

Stevens, B R; Fernandez, A; Hirayama, B; Wright, E M; Kempner, E S ^[1]

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1. Univ. of Florida, Gainesville (USA)

The functional unit molecular size of the intestinal brush border membrane-bound Na+/glucose cotransporter was determined by radiation inactivation. Purified brush border membrane vesicles preserved in cryoprotectant buffer were irradiated (-135 degrees C) with high-energy electrons from a 13-MeV (1 eV = 1.602 x 10(-19) J) linear accelerator at doses from 0 to 70 Mrad (1 rad = 0.01 Gy). After each dose, the cotransporter was investigated with respect to (i) Na(+)-dependent transport activity and (ii) immunologic blot analysis with antibodies against the cloned rabbit intestinal cotransporter. Increasing radiation decreased the maximal Na(+)-dependent cotransporter activity Jmax without affecting apparent Km. The size of the transporting functional unit was 290 +/- 5 kDa. Immunologic blot analysis of brush border membranes gave a single band of Mr 70,000, which decreased in intensity with increased radiation dose and gave a target size of 66 +/- 11 kDa. We conclude that activity of the intestinal Na+/glucose cotransporter in situ in the brush border membrane requires the simultaneous presence of four intact, independent, identical subunits arranged as a homotetramer.

• OSTI ID: 7025507
• Journal Information: Proceedings of the National Academy of Sciences of the United States of America; (USA), Journal Name: Proceedings of the National Academy of Sciences of the United States of America; (USA) Vol. 87:4; ISSN PNASA; ISSN 0027-8424
• Country of Publication: United States
• Language: English

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560120* -- Radiation Effects on Biochemicals
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63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
ACCELERATORS
ALDEHYDES
ALKALI METAL COMPOUNDS
ANIMALS
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MONOSACCHARIDES
ORGANIC COMPOUNDS
ORGANS
PROTEINS
RABBITS
RADIATION CHEMISTRY
RADIATION DOSES
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