Tyrosine (Tyr) sulfation represents a naturally occurring post-translational modification (PTM) which is a critical regulator of a number of important physiological and pathological processes (e.g. thrombosis, chemokine signalling and viral entry into host cells).1-3 However, the extreme acid lability of the Tyr sulfate ester linkage impedes the use of standard protein isolation and purification methodologies. As a result, in comparison to other PTMs very little is known about the structural and functional consequences of Tyr sulfation. Thus another, more robust, means of accessing homogenous sulfoform samples is required.
We have predicted that a number of thrombin-inhibiting proteins secreted by hematophagous organisms to facilitate blood feeding are sulfated on specific tyrosine residues. Through a combination of SPPS and peptide ligation technologies4-6 we have accessed a library of tick-derived antithrombotic sulfoproteins.7 In contrast to other methods of accessing these proteins through isolation from Nature or through recombinant technologies, chemical synthesis has enabled the generation of homogenous samples of individual homogeneous sulfoforms to interrogate the functional role of tyrosine sulfation. These studies have demonstrated that sulfation increases thrombin inhibitory activity by up to three orders of magnitude. Importantly, this work has demonstrated the vital importance of Tyr sulfation in the regulation of blood coagulation which may be applicable to the development of therapeutics for thromboembolic disorders.
1) New Biotechnol. 2009, 25, 299. 2) Cell 1999, 96, 667. 3) J. ACS Chem. Biol. 2014 , 9, 2074. 4) Angew. Chem. Int. Ed., 2013 52: 9723. doi:10.1002/anie.201304793. 5) J. Am. Chem. Soc. 2015, 137, 14011. 6) Chem, 2017, 2, 703 7) Nat Chem, 2017, DOI: 10.1038/nchem.2744