Structural insights into the interaction between a potent anti-inflammatory protein, vCCI, and the human CC chemokine, Eotaxin-1

J. Biol.Chem 289, 6592-6603 (2014).

 

Abstract:  Chemokines play important roles in the immune system, not only recruiting leukocytes to the site of infection and inflammation but also guiding cell homing and cell development.  The soluble poxvirus-encoded protein vCCI, a CC chemokine inhibitor, can bind to human CC chemokines tightly to impair the host immune defense.  This protein has no known homologs in eukaryotes, and may represent a potent method to stop inflammation.  Previously, our structure of the vCCI:MIP-1 complex indicated that vCCI uses negatively charged residues in -sheet II to interact with positively charged residues in the MIP-1 N-terminus, 20Ős region and 40Ős loop.  However, the interactions between vCCI and other CC chemokines have not yet been fully explored.  Here, we used NMR and fluorescence anisotropy to study the interaction between vCCI and eotaxin-1 (CCL11), a CC chemokine that is an important factor in the asthma response.  NMR results reveal that the binding pattern is very similar to the vCCI:MIP-1 complex, and suggest that electrostatic interactions provide a major contribution to binding.  Fluorescence anisotropy results on variants of eotaxin-1 further confirm the critical roles of the charged residues in eotaxin.  In addition, the binding affinity between vCCI and other wild type CC chemokines, MCP-1, MIP-1and RANTES, were determined as 1.09 nM, 1.16 nM, and 0.22 nM, respectively.  To our knowledge, this is the first work quantitatively measuring the binding affinity between vCCI and different CC chemokines.

 

Nai-Wei Kuo1 Yong-Guang Gao2, Megan S. Schill1, Nancy Isern3, Cynthia M. Dupureur4, and Patricia J. LiWang1,*

1 Molecular Cell Biology, University of California, Merced, 5200 North Lake Road, Merced, California 95343

2 Institute of Biochemistry and Cell Biology, SIBS, CAS, Shanghai, China

3 High Field NMR Facility, William R. Wiley Environmental Molecular Sciences Laboratory, Richland, WA 99352

4Department of Chemistry and Biochemistry, University of Missouri, St. Louis, St. Louis, MO 63121

 

 

Text Box: Figure: A: Model of the vCCI:eotaxin structure using the program Haddock. The cyan protein on the left is eotaxin, and the champagne protein on the right is vCCI. B: Space filling model of vCCI. Red is negative, blue is positive. C. Space filling model of eotaxin. Red is negative, blue is positive. The nicely complementary charged surfaces make it clear why vCCI is so effective at binding chemokines.