Structural state of the Na+/D-glucose cotransporter in calf kidney brush-border membranes. Target size analysis of Na+-dependent phlorizin binding and Na+-dependent D-glucose transport.
Biochim Biophys Acta
; 777(2): 201-8, 1984 Nov 07.
Article
em En
| MEDLINE
| ID: mdl-6148966
ABSTRACT
Target sizes of the renal sodium-D-glucose cotransport system in brush-border membranes of calf kidney cortex were estimated by radiation inactivation. In brush-border vesicles irradiated at -50 degrees C with 1.5 MeV electron beams, sodium-dependent phlorizin binding, and Na+-dependent D-glucose tracer exchange decreased exponentially with increasing doses of radiation (0.4-4.4 Mrad). Inactivation of phlorizin binding was due to a reduction in the number of high-affinity phlorizin binding sites but not in their affinity. The molecular weight of the Na+-dependent phlorizin binding unit was estimated to be 230 000 +/- 38 000. From the tracer exchange experiments a molecular weight of 345 000 +/- 24 500 was calculated for the D-glucose transport unit. The validity of these target size measurements was established by concomitant measurements of two brush-border enzymes, alkaline phosphatase and gamma-glutamyltransferase, whose target sizes were found to be 68 570 +/- 2670 and 73 500 +/- 2270, respectively. These findings provide further evidence for the assumption that the sodium-D-glucose cotransport system is a multimeric structure, in which distinct complexes are responsible for phlorizin binding and D-glucose translocation.
Buscar no Google
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Florizina
/
Sódio
/
Proteínas de Transporte
/
Glucose
/
Rim
Limite:
Animals
Idioma:
En
Revista:
Biochim Biophys Acta
Ano de publicação:
1984
Tipo de documento:
Article