Estimate of the number of urea transport sites in erythrocyte ghosts using a hydrophobic mercurial.

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Mannuzzu LM, Moronne MM, Macey RI

Estimate of the number of urea transport sites in erythrocyte ghosts using a hydrophobic mercurial.

J Membr Biol. 1993 Apr;133(1):85-97.

PubMed ID

8391582 [ View in PubMed

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Abstract

In this paper a variety of mercurials, including a pCMB-nitroxide analogue, were used to study urea transport in human red cell ghosts. It was determined that the rate of inhibition for pCMBS, pCMB, pCMB-nitroxide, and chlormerodrin extended over four orders of magnitude consistent with their measured oil/water partition coefficients. From these results, we concluded that a significant hydrophobic barrier limits access to the urea inhibition site, suggesting that the urea site is buried in the bilayer or in a hydrophobic region of the transporter. In contrast, the rate of water inhibition by the mercurials ranged by only a factor of four and did not correlate with their hydrophobicities. Thus, the water inhibition site may be more directly accessible via the aqueous phase. Under conditions that leave water transport unaffected, we determined that < or = 32,000 labeled sites per cell corresponded to complete inhibition of urea transport. This rules out major transmembrane proteins such as band 3, the glucose carrier, and CHIP28 as candidates for the urea transporter. In contrast, this result is consistent with the Kidd (Jk) antigen being the urea transporter with an estimated 14,000 copies per cell. From the experimental number of urea sites, a turnover number between 2-6 x 10(6) sec-1 at 22 degrees C is calculated suggesting a channel mechanism.

DrugBank Data that Cites this Article

Drug Targets

Drug	Target	Kind	Organism	Pharmacological Action	Actions
Chlormerodrin	Solute carrier family 12 member 1	Protein	Humans	Yes	Inducer	Details