An Experimental and Molecular-Modeling Study of the Binding of Linked Sulfated Tetracyclitols to FGF-1 and FGF-2

✍ Scribed by Siska Cochran; Cai Ping Li; Ian Bytheway

• Publisher: John Wiley and Sons
• Year: 2005
• Tongue: English
• Weight: 233 KB
• Volume: 6
• Category: Article
• ISSN: 1439-4227
• DOI: 10.1002/cbic.200500089

✦ Synopsis

Abstract

The experimental binding affinities of a series of linked sulfated tetracyclitols [Cyc~2~N‐R‐NCyc~2~, where Cyc=C~6~H~6~(OSO~3~Na)~3~ and R=(CH~2~)~n~ (n=2–10), p__‐xylyl or (C~2~H~4~)~2~‐Ncyc] for the fibroblast growth factors FGF‐1 and FGF‐2 have been measured by using a surface plasmon resonance assay. The__ K~D~ values range from 7.0 nM to 1.1 μM 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__ K~D~. 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__ K~D~ values at increasing protein concentrations. No changes in K~D~ 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.