Thermodynamics of Nanobody Binding to Lactose Permease
2016 (English)In: Biochemistry, ISSN 0006-2960, E-ISSN 1520-4995, Vol. 55, no 42, 5917-5926 p.Article in journal (Refereed) Published
Camelid nanobodies (Nbs) raised against the outward-facing conformer of a double-Trp mutant of the lactose permease of Escherichia coli (LacY) stabilize the permease in outward-facing conformations. Isothermal titration calorimetry is applied herein to dissect the binding thermodynamics of two Nbs, one that markedly improves access to the sugar-binding site and another that dramatically increases the affinity for galactoside. The findings presented here show that both enthalpy and entropy contribute favorably to binding of the Nbs to wild-type (WT) LacY and that binding of Nb to double-Trp mutant G46W/G262W is driven by a greater enthalpy at an entropic penalty. Thermodynamic analyses support the interpretation that WT LacY is stabilized in outward-facing conformations like the double-Trp mutant with closure of the cytoplasmic cavity through conformational selection. The LacY conformational transition required for ligand binding is reflected by a favorable entropy increase. Molecular dynamics simulations further suggest that the entropy increase likely stems from release of immobilized water molecules primarily from the cytoplasmic cavity upon closure.
Place, publisher, year, edition, pages
American Chemical Society (ACS), 2016. Vol. 55, no 42, 5917-5926 p.
Biochemistry and Molecular Biology
IdentifiersURN: urn:nbn:se:kth:diva-196984DOI: 10.1021/acs.biochem.6b00826ISI: 000386422100004ScopusID: 2-s2.0-84994031905OAI: oai:DiVA.org:kth-196984DiVA: diva2:1055936
QC 201612132016-12-132016-11-282016-12-13Bibliographically approved