Impact of Salt Bridges on the Equilibrium Binding and Adhesion of Human CD2 and CD58

Marco V Bayas,Alice Kearney,Adam Avramovic,P Anton Van Der Merwe,Deborah E Leckband

doi:10.1074/jbc.m607968200

Marco V Bayas, Alice Kearney + Show 3 more

Open Access

https://doi.org/10.1074/jbc.m607968200

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Abstract

This study describes quantitative investigations of the impact of single charge mutations on equilibrium binding, kinetics, and the adhesion strength of the CD2-CD58 interaction. Previously steered molecular dynamics simulations guided the selection of the charge mutants investigated, which include the CD2 mutants D31A, K41A, K51A, and K91A. This set includes mutations in which the previous cell aggregation and binding data either agreed or disagreed with the steered molecular dynamics predictions. Surface plasmon resonance measurements quantified the solution binding properties. Adhesion was quantified with the surface force apparatus, which was used previously to study the closely related CD2-CD48 interaction. The results reveal roles that these salt bridges play in equilibrium binding and adhesion. We discuss both the molecular basis of this behavior and its implications for cell adhesion.

Highlights

The recognition of antigen-presenting cells by T-cells, in the adaptive immune response, involves the simultaneous interaction of large arrays of low affinity surface proteins [1, 2]
The results reveal roles that these salt bridges play in equilibrium binding and adhesion
To determine the role of these salt bridges in binding equilibria and cell aggregation, different groups have investigated the impact of point mutations on the CD2/CD58 binding affinity and on cell aggregation as measured by erythrocyte rosette formation

Summary

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C C NC NC NC C C NC Transient a Data are from Ref. 8. b Data are from Ref. 31. c Data are from Ref. 13: C, critical; NC, non-critical; ND, not done. C C NC NC NC C C NC Transient a Data are from Ref. 8. C Data are from Ref. 13: C, critical; NC, non-critical; ND, not done. Lys-91 formed a transient salt bridge during the simulated detachment. Lular junctions, where there is dynamic exchange between bound and unbound states. This is distinctly different from single molecule behavior. We report a quantitative investigation of the impact of single charge mutations on equilibrium binding, kinetics, and the adhesion strength of the CD2-CD58 interaction. Steered molecular dynamics simulations [13] guided the selection of the charge mutants investigated, which include the CD2

EXPERIMENTAL PROCEDURES

RESULTS

DISCUSSION