2 research outputs found
Targeting the CRD Fâface of human galectinâ3 and allosterically modulating glycan binding by angiostatic PTX008 and a structurally optimized derivative
12 p.-8 fig.Calix[4]arene PTX008 is an angiostatic agent that inhibits tumor growth in mice by binding to galectinâ1, a ÎČâgalactosideâbinding lectin. To assess the affinity profile of PTX008 for galectins, we used 15N,1H HSQC NMR spectroscopy to show that PTX008 also binds to galectinâ3 (Galâ3), albeit more weakly. We identified the contact site for PTX008 on the Fâface of the Galâ3 carbohydrate recognition domain. STD NMR revealed that the hydrophobic phenyl ring crown of the calixarene is the binding epitope. With this information, we performed molecular modeling of the complex to assist in improving the rather low affinity of PTX008 for Galâ3. By removing the Nâdimethyl alkyl chain amide groups, we produced PTX013 whose reduced alkyl chain length and polar character led to an approximately eightfold stronger binding than PTX008. PTX013 also binds Galâ1 more strongly than PTX008, whereas neither interacts strongly, if at all, with Galâ7. In addition, PTX013, like PTX008, is an allosteric inhibitor of galectin binding to the canonical ligand lactose. This study broadens the scope for galectin targeting by calixareneâbased compounds and opens the perspective for selective galectin blocking.K.H.M. is grateful to the Ludwigs-Maximillians-UniversitĂ€t (LMU) Center for Advanced Study, as well as to the Alexander von Humboldt Stiftung, for financial support during his sabbatical stay at LMU in Munich, Germany. K.H.M. also holds a van der Laar
Visiting Professorship in Structural Biology at Maastricht University,Netherlands. K.H.M. acknowledges that NMR instrumentation was provided with funds from the National Science Foundation(BIR-961477), the University of Minnesota Medical School, and the Minnesota Medical Foundation.Peer reviewe