Structural Basis of Receptor Sulfotyrosine Recognition by a CC Chemokine: The N-Terminal Region of CCR3 Bound to CCL11/Eotaxin-1

Abstract

Trafficking of leukocytes in immune surveillance and inflammatory responses is activated by chemokines engaging their receptors. Sulfation of tyrosine residues in peptides derived from the eosinophil chemokine receptor CCR3 dramatically enhances binding to cognate chemokines. We report the structural basis of this recognition and affinity enhancement. We describe the structure of a CC chemokine (CCL11/eotaxin-1) bound to a fragment of a chemokine receptor: residues 8–23 of CCR3, including two sulfotyrosine residues. We also show that intact CCR3 is sulfated and sulfation enhances receptor activity. The CCR3 sulfotyrosine residues form hydrophobic, salt bridge and cation-p interactions with residues that are highly conserved in CC chemokines. However, the orientation of the chemokine relative to the receptor N terminus differs substantially from those observed for two CXC chemokines, suggesting that initial binding of the receptor sulfotyrosine residues guides subsequent steps in receptor activation, thereby influencing the receptor conformational changes and signaling.

Homogeneous Sulfopeptides and Sulfoproteins: Synthetic Approaches and Applications To Characterize the Effects of Tyrosine Sulfation on Biochemical Function

“…44,46 In both cases, the primary binding site for receptor sulfotyrosine is the N-loop/β3 cleft, and the structures reveal specific salt bridges, hydrogen bonds, hydrophobic interactions, and cation−π interactions involved in sulfotyrosine recognition ( Figure 3A,B). However, these structures also highlight some potentially important differences between the chemokine/receptor pairs.…”

Chemokines and Bone

“…Tyrosine sulfation is a posttranslational modification that increases both the binding affinity and potency of chemokines to their cognate receptors. Recently, the structure of a CCL11 (eotaxin-1) bound to a fragment of CCR3 that included two sulfotyrosine residues was solved [9]. Sulfotyrosine residues within the receptor formed hydrophobic, salt bridge, and cation-p interactions with highly conserved residues in the chemokine.…”

Chemokine-Receptor Interactions: Solving the Puzzle, Piece by Piece

“…In this issue of Structure, Millard et al (2014) report the first structure of a CC chemokine in complex with a receptor peptide, namely the chemokine CCL11 (eotaxin-1) with a sulfated peptide (Su1617) derived from the N terminus of the receptor CCR3. The researchers have obtained 55 intermolecular contacts (as well as numerous intramolecular contacts), leading to a complex structure with a clearly delineated binding surface on the chemokine for its receptor, composed of the N-loop and b2-b3 region from CCL11 (Figure 1).…”

“…In the current structure, the Phe11 residue does not appear to make direct contact with the receptor peptide. It is also noted that chemokines bind to intact receptors Millard et al (2014) CCL11 is shown as a space filling model with critical basic residues Arg 16, Arg 22, and Lys 47 highlighted in blue. The receptor peptide from CCR3 (Su1617) is shown in magenta, and its two sulfated tyrosine residues are shown as balls and sticks, clearly interacting with CCL11.…”

“…The receptor peptide from CCR3 (Su1617) is shown in magenta, and its two sulfated tyrosine residues are shown as balls and sticks, clearly interacting with CCL11. The structure of the CCR5 receptor (Protein Data Bank [PDB] ID 4MBS, the only known high resolution CC chemokine receptor structure yet reported) is shown below CCL11 to indicate the orientation of the chemokine relative to its receptor as implied by the structure reported by Millard et al (2014) (PDB ID 2MPM). The dotted magenta line indicates the possible trajectory of the N terminus of the receptor as it binds a chemokine ligand.…”