Synthesis of disulfated peptides corresponding to the N -terminus of chemokines receptors CXCR6 (CXCR6 1-20 ) and DARC (DARC 8-42 ) using a sulfate-protecting group strategy
ABSTRACT Tyrosine sulfation is a post translational modification that occurs on integral membrane and secreted proteins, and is required for mediating crucial biological processes. Until recently the synthesis of sTyr peptides, especially those containing multiple sTyr residues, were among the most challenging peptides to prepare. We recently described an efficient strategy for Fmoc-based solid phase synthesis of sTyr peptides in which the sulfate group in the sTyr residue(s) is protected with a DCV group (FmocTyr(SO(3)DCV)OH, 1). After cleavage of the peptide from the support the DCV group is removed by hydrogenolysis. Here we demonstrate that sTyr peptides containing Met or Trp residues can be prepared using our sulfate-protecting group strategy by preparing peptides corresponding to residues 1-20 of chemokine receptor CXCR6 and 8-42 of chemokine receptor DARC. Removing the DCV groups at the end of the syntheses was readily achieved, without any reduction of the indole ring in Trp, by performing the hydrogenolysis in the presence of triethylamine. These conditions were found to be particularly efficient for removing the DCV group and superiour to our original conditions using H(2), ammonium formate, Pd/C. The presence of Met was found not to interfere with the removal of the DCV group. The use of pseudoproline dipeptides and N-backbone protection with the 2,4-dimethoxybenzyl group were found to be very effective tactics for preventing aggregation and aspartimide formation during the synthesis of these peptides. We also report an alternative and more cost effective synthesis of amino acid 1.
SourceAvailable from: Ayman El-FahamChemInform 11/2011; 67(45):8595-8606. DOI:10.1016/j.tet.2011.08.046
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ABSTRACT: Tyrosine (Tyr) sulfation is a common post-translational modification that is implicated in a variety of important biological processes, including the fusion and entry of human immunodeficiency virus type-1 (HIV-1). A number of sulfated Tyr (sTyr) residues on the N-terminus of the CCR5 chemokine receptor are involved in a crucial binding interaction with the gp120 HIV-1 envelope glycoprotein. Despite the established importance of these sTyr residues, the exact structural and functional role of this post-translational modification in HIV-1 infection is not fully understood. Detailed biological studies are hindered in part by the difficulty in accessing homogeneous sulfopeptides and sulfoproteins through biological expression and established synthetic techniques. Herein we describe an efficient approach to the synthesis of sulfopeptides bearing discrete sulfation patterns through the divergent, site-selective incorporation of sTyr residues on solid support. By employing three orthogonally protected Tyr building blocks and a solid-phase sulfation protocol, we demonstrate the synthesis of a library of target N-terminal CCR5(2-22) sulfoforms bearing discrete and differential sulfation at Tyr10, Tyr14 and Tyr15, from a single resin-bound intermediate. We demonstrate the importance of distinct sites of Tyr sulfation in binding gp120 through a competitive binding assay between the synthetic CCR5 sulfopeptides and an anti-gp120 monoclonal antibody. These studies revealed a critical role of sulfation at Tyr14 for binding and a possible additional role for sulfation at Tyr10. N-terminal CCR5 variants bearing a sTyr residue at position 14 were also found to complement viral entry into cells expressing an N-terminally truncated CCR5 receptor.ACS Chemical Biology 06/2014; 9(9). DOI:10.1021/cb500337r · 5.36 Impact Factor
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ABSTRACT: Template-constrained cyclic sulfopeptides that inhibit HIV-1 entry were rationally designed based on a loop from monoclonal antibody (mAb) 412d. A focused set of sulfopeptides was synthesized using Fmoc-Tyr(SO3DCV)-OH (DCV = 2,2-dichlorovinyl). Three cyclic sulfopeptides that inhibit entry of HIV-1 and complement the activity of known CCR5 antagonists were identified.Organic & Biomolecular Chemistry 09/2013; DOI:10.1039/c3ob41395k · 3.49 Impact Factor