HIGH-RESOLUTION SOLUTION STRUCTURE OF BASIC FIBROBLAST GROWTH-FACTOR DETERMINED BY MULTIDIMENSIONAL HETERONUCLEAR MAGNETIC-RESONANCE SPECTROSCOPY

The high-resolution solution structure of recombinant human basic fibr oblast growth factor (FGF-2), a protein of 17.2 kDa that exhibits a va riety of functions related to cell growth and differentiation, has bee n determined using three-dimensional heteronuclear NMR spectroscopy. A total of 30 structures were calculated by means of hybrid distance ge ometry-simulated annealing using a total of 2865 experimental NMR rest raints, consisting of 2486 approximate interproton distance restraints , 50 distance restraints for 25 backbone hydrogen bonds, and 329 torsi on angle restraints. The atomic rms distribution about the mean coordi nate positions for the 30 structures for residues 29-152 is 0.43 +/- 0 .03 Angstrom for the backbone atoms, 0.83 +/- 0.05 Angstrom for all at oms, and 0.51 +/- 0.04 Angstrom for ail atoms excluding disordered sid e chains. The overall structure of FGF-2 consists of 11 extended antip arallel beta-strands arranged in three groups of three or four strands connected by tight turns and loop regions creating a pseudo-3-fold sy mmetry. Two strands from each group come together to form a beta-sheet barrel of six antiparallel beta-strands, A helix-like structure was o bserved for residues 131-136, which is part of the heparin binding sit e (residues 128-138). The discovery of the helix-like region in the pr imary heparin binding site instead of the beta-strand conformation des cribed in the X-ray structures may have important implications in unde rstanding the nature of heparin-FGF-2 interactions. A total of seven t ightly bound water molecules were found in the FGF-2 structure, two of which are located in the heparin binding site, The first 28 N-termina l residues appear to be disordered, which is consistent with previous X-ray structures. A best fit superposition of the NMR structure of FGF -2 with the 1.9 Angstrom resolution X-ray structure by Zhu et al. (199 1) yields a backbone atomic rms difference of 0.94 Angstrom, indicativ e of a dose similarity between the NMR and X-ray structures.