THE STRUCTURE AND DYNAMICS OF HUMAN INTERLEUKIN-4 IN SOLUTION

The structure and dynamics of human interleukin-4 in solution have bee n studied using multi-dimensional nuclear magnetic resonance (NMR) spe ctroscopy. The protein adopts a four-helix bundle conformation with a left-handed up-up-down-down topology. N-15 NMR relaxation studies show that the helical core of the protein exists as a well-defined structu re with limited conformational flexibility while the loops that connec t the helices experience substantial fluctuations on a fast time scale . Interleukin-4 undergoes a partial unfolding transition at low pH. Th is partly unfolded state of the protein has some of the characteristic s of a ''molten globule'' state.