Eotaxin is a member of the chemokine family of
about 40 proteins that induce cell migration. Eotaxin binds
the CC chemokine receptor CCR3 that is highly expressed
by eosinophils, and it is considered important in the pathology
of chronic respiratory disorders such as asthma. The high
resolution structure of eotaxin is known. The 74 amino
acid protein has two disulfide bridges and shows a typical
chemokine fold comprised of a core of three antiparallel
β-strands and an overlying α-helix. In this paper,
we report the backbone dynamics of eotaxin determined through
15N-T1, T2,
and {1H}-15N nuclear Overhauser effect
heteronuclear multidimensional NMR experiments. This is
the first extensive study of the dynamics of a chemokine
derived from 600, 500, and 300 MHz NMR field strengths.
From the T1, T2,
and NOE relaxation data, parameters that describe the internal
motions of eotaxin were derived using the Lipari–Szabo
model free analysis. The most ordered regions of the protein
correspond to the known secondary structure elements. However,
surrounding the core, the regions known to be functionally
important in chemokines show a range of motions on varying
timescales. These include extensive subnanosecond to picosecond
motions in the N-terminus, C-terminus, and the N-loop succeeding
the disulfides. Analysis of rotational diffusion anisotropy
of eotaxin and chemical exchange terms at multiple fields
also allowed the confident identification of slow conformational
exchange through the “30s” loop, disulfides,
and adjacent residues. In addition, we show that these
motions may be attenuated in the dimeric form of a synthetic
eotaxin. The structure and dynamical basis for eotaxin
receptor binding is discussed in light of the dynamics
data.