1H NMR solution structure of an active monomeric interleukin-8

The solution structure of a monomeric form of interleukin-8 (IL-8) has been solved using 1H NMR spectroscopy. The chemically synthesized nonnatural analog [IL-8 (4-72) L25 NH-->NCH3] has the same activity as that of native IL-8. Thirty structures were generated using the hybrid distance geometry and simulated annealing protocol using the program X-PLOR. The structure is well-defined except for N-terminal residues 4-6 and C-terminal residues 67-72. The rms distribution about the average structure for residues 7-66 is 0.38 A for the backbone atoms and 0.87 A for all heavy atoms. The structure consists of a series of turns and loops followed by a triple-stranded beta sheet and a C-terminal alpha helix. The structure of the monomer is largely similar to the native dimeric IL-8 structures previously determined by both NMR and X-ray methods. The major difference is that, in the monomeric analog, the C-terminal residues 67-72 are disordered whereas they are helical in the two dimeric structures. The best fit superposition of the backbone atoms of residues 7-66 of the monomer structure on the dimeric IL-8 structures showed rms differences of 1.5 and 1.2 A respectively. The turn (residues 31-35), which is disulfide linked to the N-terminal region, adopts a conformation in the monomer similar to that seen in the dimeric X-ray structure (rms difference 1.4 A) and different from that seen in the dimeric NMR structure (rms difference 2.7 A).(ABSTRACT TRUNCATED AT 250 WORDS)