Characterization of chicken cystatin binding to rat renal brush-border membranes |
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Authors: | Konopska Bogus?awa Gburek Jakub Go?ab Krzysztof Warwas Maria |
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Institution: | aDepartment of Pharmaceutical Biochemistry, Wrocław Medical University, Szewska 38/39, 50-139 Wrocław, Poland |
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Abstract: | Chicken cystatin, a homologue of human cystatin C, like other low-molecular-weight proteins is metabolized by renal proximal tubule cells. However, the precise mechanism(s) of this process has not been elucidated yet. To characterize chicken cystatin binding to renal brush-border membranes, the incubation of fluorescein labelled protein with rat cortical homogenate was performed. Saturation-dependent and reversible binding with low affinity (Kd = 3.67–4.07 μM) and high capacity (Bmax = 2.32–2.79 nmol/mg) was observed. Bovine albumin was the most potent competitor (Ki = 0.7 μM) among other megalin/cubilin ligands tested. The presence of Ca+ 2 ions was necessary to effective cystatin binding by brush-border membranes. Obtained data strongly support the hypothesis that chicken cystatin is a novel ligand for megalin/cubilin receptors tandem on proximal tubular cells. |
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Keywords: | Chicken cystatin Renal brush-border membranes Megalin ligands |
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