The effect of the iron saturation of transferrin on its binding and uptake by rabbit reticulocytes

Research output: Contribution to journalArticlepeer-review

Authors

Colleges, School and Institutes

Abstract

Polyacrylamide-gel electrophoresis in urea was used to prepare the four molecular species of transferrin:diferric transferrin, apotransferrin and the two monoferric transferrins with either the C-terminal or the N-terminal metal-binding site occupied. The interaction of these 125I-labelled proteins with rabbit reticulocytes was investigated. At 4 degrees C the average value for the association constant for the binding of transferrin to reticulocytes was found to increase with increasing iron content of the protein. The association constant for apotransferrin binding was 4.6 X 10(6)M-1, for monoferric (C-terminal iron) 2.5 X 10(7)M-1, for monoferric (N-terminal iron) 2.8 X 10(7)M-1 and for diferric transferrin, 1.1 X 10(8)M-1. These differences in the association constants did not affect the processing of the transferrin species by the cells at 37 degrees C. Accessibility of the proteins to extracellular proteinase indicated that the transferrin was internalized by the cells regardless of the iron content of the protein, since in each case 70% was inaccessible. Cycling of the cellular receptors may also occur in the absence of bound transferrin.

Details

Original languageEnglish
Pages (from-to)505-10
Number of pages6
JournalBiochemical Journal
Volume219
Issue number2
Publication statusPublished - 15 Apr 1984

Keywords

  • Animals, Transferrin, Electrophoresis, Polyacrylamide Gel, Pronase, Kinetics, Rabbits, Reticulocytes, Protein Binding, Iron, Apoproteins, Binding Sites