THE 3-DIMENSIONAL SOLUTION STRUCTURE OF RANTES

The solution structure of the chemokine RANTES (regulated on activatio n, normal T-cell expressed and secreted) has been determined using NMR spectroscopy. Backbone and side-chain H-1 and N-15 assignments have b een obtained using a combination of two-dimensional homonuclear and th ree-dimensional heteronuclear spectra, Regular elements of secondary s tructure have been identified on the basis of a qualitative interpreta tion of NOE data, J(NH-H alpha) coupling constants, and amide exchange rates. Three-dimensional structures were calculated from a total of 2 146 experimental restraints using a combination of distance geometry a nd simulated annealing protocols. For the 13 best structures the avera ge backbone (N, C alpha, C) atomic rmsd from the mean coordinates for residues 5-65 is 0.64 Angstrom (+/-0.14 Angstrom) for the dimer and 0. 50 Angstrom (+/-0.08 Angstrom) for the individual monomers. Each monom er consists of a three-stranded antiparallel P-sheet (residues 26-30, 38-43, 48-51) in a Greek key motif with a C-terminal helix (56-65) pac ked across the sheet, an arrangement similar to the monomeric structur e of other members of this chemokine family (IL-8, PF4, MGSA/Gro alpha , and MIP-1 beta). Overall, the RANTES dimer resembles that previously reported for MIP-1 beta.