Post-Translational Modification by Tyrosine Sulfation and Its Functions

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Tyrosine sulfation is an important post-translational modification with a range of functional relevancies, and for those proteins that are sulfated in nature, this modification could be indispensable for the implication of their function. It is known that when sulfated proteins are expressed in bacteria or yeast, the resultant proteins are not tyrosine-sulfated due to the lack of this modification in those vectors, and hence the in vitro tyrosine-sulfation of recombinant proteins by tyrosylprotein sulfotransferase (TPST) would be a valuable tool in converting proteins so produced to their natural form. Hirudin, a potent thrombin inhibitor secreted by the medicinal leech, Hirudo medicinalis, requires sulfation of its 63rd tyrosine for exertion of its fullest activity as a thrombin inhibitor. Recombinant hirudin, expressed in bacteria or yeast is not tyrosine sulfated.For the post-translational modification of recombinant hirudin, TPST was prepared from a bovine liver Golgi preparation. TPST was able to sulfate recombinant hirudin variant 1 (rHV-1) expressed in Escherichia coli and the C-terminal hirudin fragment 54-65 but not the N-terminal hirudin fragment 1-15, indicating its specificity for the naturally sulfated tyrosine 63.