Dynamic strength of the interaction between lung surfactant protein D (SP-D) and saccharide ligands.
In order to investigate the dynamic strength of the interaction between lung surfactant protein D (SP-D) and different sugars, maltose, mannose, glucose, and galactose, we have used an atomic force microscope to monitor the interaction on a single molecule scale. The experiment is performed by measuring the rupture force when the SP-D-sugar bond is subjected to a continuously increasing force. Under these dynamic conditions, SP-D binds strongest to d-mannose and weakest to maltose and d-galactose. These results differ from equilibrium measurements wherein SP-D exhibits preference for maltose. On the basis of this finding, we propose that the binding of the disaccharide maltose to SP-D, which is energetically stronger than the binding of any of the monosacchrides, alters the structure of the binding site in a way that lowers the dynamic strength of the bond. We conclude that determining the strength of a protein-ligand bond under dynamic stress using an atomic force microscope is possibly more relevant for mimicking the actual nonequilibrium physiological situation in the lungs.
Thormann
Esben
E
MEMPHYS, Department of Physics and Chemistry, University of Southern Denmark, Campusvej 55, DK-5230 Odense M, Denmark. esbent@memphys.sdu.dk
Dreyer
Jakob K
JK
Simonsen
Adam C
AC
Hansen
Per L
PL
Hansen
Søren
S
Holmskov
Uffe
U
Mouritsen
Ole G
OG
D002241:Carbohydrates / Q000737:chemistry*; D002846:Chromatography, Affinity; D002852:Chromatography, Ion Exchange; D004797:Enzyme-Linked Immunosorbent Assay; D008024:Ligands; D008168:Lung / Q000737:chemistry*; D018625:Microscopy, Atomic Force; D011485:Protein Binding; D037663:Pulmonary Surfactant-Associated Protein D / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism
D002241:Carbohydrates; D008024:Ligands; D037663:Pulmonary Surfactant-Associated Protein D