An experimental and molecular-modeling study of the binding of linked sulfated tetracyclitols to FGF-1 and FGF-2.
The experimental binding affinities of a series of linked sulfated tetracyclitols [Cyc2N-R-NCyc2, where Cyc = C6H6(OSO3Na)3 and R = (CH2)n (n = 2-10), p-xylyl or (C2H4)2-Ncyc] for the fibroblast growth factors FGF-1 and FGF-2 have been measured by using a surface plasmon resonance assay. The KD values range from 7.0 nM to 1.1 microM for the alkyl-linked ligands. The binding affinity is independent of the flexibility of the linker, as replacement of the alkyl linker with a rigid p-xylyl group did not affect the KD. Calculations suggest that binding modes for the p-xylyl-linked ligand are similar to those calculated for the flexible alkyl-linked tetracyclitols. The possible formation of cross-linked FGF:cyclitol complexes was examined by determining KD values at increasing protein concentrations. No changes in KD were observed; this suggesting that only 1:1 complexes are formed under these assay conditions. Monte Carlo multiple-minima calculations of low-energy conformers of the FGF-bound ligands showed that all of the sulfated tetracyclitol ligands can bind effectively in the heparan sulfate-binding sites of FGF-1 and FGF-2. Binding affinities of these complexes were estimated by the Linear Interaction Energy (LIE) method to within a root-mean-square deviation of 1 kcal mol(-1) of the observed values. The effect of incorporating cations to balance the overall charge of the complexes during the LIE calculations was also explored.
Cochran
Siska
S
Drug Design Group, Progen Industries Ltd. P.O. Box 28, Richlands BC, Queensland 4077, Australia.
Li
Cai Ping
CP
Bytheway
Ian
I
D040761:Biomimetic Materials / Q000737:chemistry / Q000378:metabolism; D019295:Computational Biology; D003510:Cyclohexanes / Q000737:chemistry / Q000378:metabolism*; D053138:Cyclohexenes; D016220:Fibroblast Growth Factor 1 / Q000737:chemistry / Q000378:metabolism*; D016222:Fibroblast Growth Factor 2 / Q000737:chemistry / Q000378:metabolism*; D006493:Heparin / Q000031:analogs & derivatives / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D008958:Models, Molecular; D009010:Monte Carlo Method; D011485:Protein Binding; D011509:Proteoglycans / Q000737:chemistry / Q000378:metabolism; D013431:Sulfates / Q000378:metabolism*; D020349:Surface Plasmon Resonance; D013816:Thermodynamics
D003510:Cyclohexanes; D053138:Cyclohexenes; D011509:Proteoglycans; D013431:Sulfates; C036090:heparin proteoglycan; D016222:Fibroblast Growth Factor 2; D016220:Fibroblast Growth Factor 1; C052568:cyclohexene; D006493:Heparin