Phaseolus vulgaris isolectin binding to human erythrocytes

The Phaseolus vulgaris isolectins L4,L3E1, L2E2, L1E3, and E4 were isolated by affinity and ion exchange chromatography. Pure isolectins were radiolabeled by the chloramine-T method with Na125IO4 and their binding to human erythrocytes was studied. A normal erythrocyte has approximately 8 times 10(5...

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Bibliographic Details
Published in:The Journal of biological chemistry 1979-02, Vol.254 (3), p.894-898
Main Authors: Egorin, M J, Bachur, S Z, Felsted, R L, Leavitt, R D, Bachur, N R
Format: Article
Language:English
Subjects:
Binding Sites
Binding, Competitive
Erythrocytes - metabolism
Humans
Immunodiffusion
Kinetics
Lectins
Protein Binding
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Summary:The Phaseolus vulgaris isolectins L4,L3E1, L2E2, L1E3, and E4 were isolated by affinity and ion exchange chromatography. Pure isolectins were radiolabeled by the chloramine-T method with Na125IO4 and their binding to human erythrocytes was studied. A normal erythrocyte has approximately 8 times 10(5) receptor sites for each isolectin; however, the association constants (Ka) of binding increased from 1.1 times 10(7) M-1 to 3.8 times 10(8) M-1, with increasing number of E subunits per tetrameric isolectin molecule. Isolectin to erythrocyte binding reached equilibrium rapidly and was reversed by fetuin. All isolectins competed with 125I-E4 for erythrocyte binding sites, with a constant (KI) similar to the Ka calculated for each respective radiolabeled isolectin. When isolectin binding at 0 degrees C, 4 degrees C, or 8 degrees C was compared to that at 25 degrees C, there was no reduction in the number of binding sites per cell, but the Ka of E4 was reduced to 3 times 10(7) M-1. Fixed erythrocytes displayed similar isolectin binding characteristics.
ISSN:0021-9258
1083-351X
DOI:10.1016/S0021-9258(17)37888-2