Structural identification of brush border membrane transport systems--towards an understanding of regulatory mechanisms.

Until recently proximal tubular membrane transport systems were defined only on the basis of their function. However, in the past 4-5 years the use of molecular biology techniques has permitted structural identification of several proximal tubular transport systems. For example, sodium/D-glucose, sodium/phosphate, and sodium/sulfate cotransport systems have been identified. Also (a component of) an amino acid transport system accepting cystine and dibasic amino acids has been identified. These transport pathways may be targets for genetic alterations in proximal tubular solute reabsorption and/or be under physiological control.