Nuclear magnetic resonance solution structure of truncated human GRO beta [5-73] and its structural comparison with CXC chemokine family members GRO alpha and IL-8

The three-dimensional structure of a novel four amino acid truncated form o f the CXC chemokine GRO beta [5-73] isolated from bone marrow stromal cells with potent hematopoietic and anti-infective activities has been determine d by two-dimensional IH nuclear magnetic resonance (NMR) spectroscopy in so lution. On the basis of 1878 upper distance constraints derived from nuclea r Overhauser effects (NOE) and 314 dihedral angle constraints, a group of 2 0 conformers representing the solution structure of the human GRO beta [5-7 3] was computed with the program DYANA. At the concentrations used for NMR study, GRO beta [5-73] forms a dimer in solution that is architectured by a six-stranded antiparallel beta-sheet (residues 25 to 29, 39 to 44, 49 to 5 2) and a pair of helices (residues 58 to 68) with 2-fold symmetry, while th e C terminus of the protein is disordered. The average of the pairwise root -mean-square deviations of individual NMR conformers relative to the mean c oordinates for the backbone atoms N, C-alpha and C' of residues 5 to 68 is 0.47 Angstrom. Overall, the global fold of GRO beta [5-73] is similar to th at of the previously reported NMR structure of GRO alpha and the NMR and X- ray structures of interleukin-8. Among these three CXC chemokines, GRO beta [5-73] is most similar in structure to GRO alpha. Significant differences between GRO beta [5-73], GRO alpha and interleukin-8 are in the N-terminal loop comprising residues 12 to 19. The N-terminal arm containing the conser ved ELR motif and the loop of residues 30 to 38 containing the GPH motif ar e different among these three CXC chemokines. The structural differences in these two regions may be responsible for the specificity of the receptor b inding and biological activity of different chemokines. (C) 1999 Academic P ress.