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Description:
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Chemokines (chemotactic cytokines ) comprise a large family of proteins that
recruit and activate leukocytes , giving chemokines a major role in both immune response
and inflammation -related diseases . Viral CC chemokine inhibitor (vCCI ) is a poxvirus
encoded protein that has been shown to bind tightly and inhibit the action of many CC
chemokines . This function suggests that vCCI could be explored as an antiinflammatory
therapeutic , a possibility that has been supported in mouse studies . The
structure of vCCI in unbound form was determined by others , but to date no structure
has been reported of bound vCCI . We report the NMR structure of vCCI in complex
with the human CC chemokine MIP -1[beta] . The non -aggregating MIP -1[beta] variant MIP -1[beta]
45AASA48 was used in this complex to allow sufficiently high concentration at pH 7 to
carry out the solution structure determination . A combination of NOE distance
restraints , torsion angle restraints , and residual dipolar coupling were used to determine
the structure of the complex , which also required protein deuteration due to its relatively
large size (34kDa ) . The structure shows that MIP -1[beta] binds to vCCI with 1 :1 stoichiometry , forming a complex of 311 amino acids . vCCI uses residues from its [beta] -
sheet II to interact with a surface of MIP -1[beta] that includes residues adjacent to its Nterminus ,
as well as residues in the 20's region , and the 40's loop . The structure of the
MIP -1[beta] -vCCI complex reveals for the first time the regions of each protein involved in
the interaction , and allows a greater understanding of the strategy used by vCCI to
tightly bind numerous chemokines , while retaining selectivity for the CC chemokine
subfamily . |