Structural Insights into the Interaction between a Potent Anti-inflammatory Protein, Viral CC Chemokine Inhibitor (vCCI), and the Human CC Chemokine, Eotaxin-1

• Published in: The Journal of biological chemistry 2014-03, Vol.289 (10), p.6592-6603
• Main Authors: Kuo, Nai-Wei, Gao, Yong-Guang, Schill, Megan S., Isern, Nancy, Dupureur, Cynthia M., LiWang, Patricia J.
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Anti-inflammatory Protein; Biophysics; Chemokine CCL11 - chemistry; Chemokine CCL11 - genetics; Chemokine CCL11 - immunology; Chemokine CCL2 - chemistry; Chemokine CCL2 - immunology; Chemokine CCL4 - chemistry; Chemokine CCL4 - immunology; Chemokine CCL5 - chemistry; Chemokine CCL5 - immunology; Chemokine-binding Protein; Chemokines; Eotaxin; Fluorescence Anisotropy; Humans; Inflammation - immunology; Molecular Docking; Molecular Sequence Data; NMR; Nuclear Magnetic Resonance, Biomolecular; Protein Binding - immunology; Protein Structure and Folding; Protein Structure, Secondary; Protein-Protein Interactions; vCCI; Viral Proteins - chemistry; Viral Proteins - immunology; Virulence Factors - chemistry; Virulence Factors - immunology
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M113.538991

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 viral CC chemokine inhibitor (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-1β (macrophage inflammatory protein-1β) complex indicated that vCCI uses negatively charged residues in β-sheet II to interact with positively charged residues in the MIP-1β N terminus, 20s region and 40s 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-1β 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-1. In addition, the binding affinity between vCCI and other wild type CC chemokines, MCP-1 (monocyte chemoattractant protein-1), MIP-1β, and RANTES (regulated on activation normal T cell expressed and secreted), were determined as 1.1, 1.2, and 0.22 nm, respectively. To our knowledge, this is the first work quantitatively measuring the binding affinity between vCCI and multiple CC chemokines. Background: The mechanism used by viral protein vCCI to tightly bind to many CC chemokines is not known. Results: Specific positively charged residues in the chemokine eotaxin-1 mediate binding to vCCI. Conclusion: Basic residues in the chemokine each provide incremental affinity for vCCI. Significance: This work shows how vCCI can bind a variety of CC chemokines.