Comparative 19F-NMR studies of fluororetinol analogs with rat cellular retinol binding protein II (CRBP II) and rat cellular retinol-binding protein (CRBP) were performed to probe differences in the binding interactions of these two homologous proteins. Line shape analyses of 19F-NMR spectra of (E,E,Z,E)-6-fluoro-9-(4-methoxy-2,3,6-trimethylphenyl)-3,7-dimethyl-2,4,6,8-nonatetren-1-ol (ligand 1), (E,E,Z,E)-6-fluoro-9-(2,2′dimethyl-6-ethylcyclohexenyl)-3,7-dimethyl-2,4,6,8-nonatetren-1-ol (ligand 2), (E,Z,E,E)-5-fluoro-9-(2,2′-dimethyl-6-methylcyclohexenyl)-3,7-dimethyl-2,4,6,8-nonatetren-l-ol (ligand 3), when complexed with CRBP II at temperatures ranging from 0-45°C, revealed that the 19F resonances corresponding to the bound ligand were in slow chemical exchange between two resonance frequencies. This was further supported by a 2D-NOESY exchange experiment. The kex at 25°C was estimated from spectral simulation and fitting analyses to be 887 s±1, 1010 s±1and 771 s±1 for CRBP II complexed 1, 2, and 3, respectively. In contrast, only a single absorption was observed for bound ligands complexed with rat CRBP over this temperature range, suggesting that the conformational dynamics of retinol binding are differeut for these two closely homologous proteins.
|Original language||English (US)|
|Number of pages||9|
|Journal||Biochimica et Biophysica Acta (BBA)/Protein Structure and Molecular|
|State||Published - Sep 21 1994|
Bibliographical noteFunding Information:
This work was supported by National Institutes of Health grants DK40172 and DK45755. NMR spectra were collected at the Washington University High Resolution NMR Service Facility which is funded in part through a NIH Biomedical Research Support Shared Instrument Grant LRR02004 and RR05018). E. Li is a recipient on an NIH RCDA (DK02072). We wish to thank Dr. Ira Ropson for helpful discussions on the DNMR5 program.
- Cellular retinol binding protein