, Volume 405, Issue 4, pp 1425-1429

Fluorescence assay for protein post-translational tyrosine sulfation

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Abstract

We developed a fluorescent assay to conveniently determine the kinetics of protein sulfation, which is essential for understanding interface between protein sulfation and protein–protein interactions. Tyrosylprotein sulfotransferase (TPST) catalyzes protein sulfation using 3′-phosphate 5′-phosphosulfate (PAPS) as sulfuryl group donor. In this report, PAPS was regenerated following sulfuryl group transfer between adenosine 3′,5′-diphosphate and 4-methylumbelliferyl sulfate catalyzed by phenol sulfotransferase (PST). The TPST and PST coupled enzyme platform continuously generated fluorescent 4-methylumbelliferone (MU) that was used to real-time monitor protein sulfation. Using a recombinant N utilization substance protein A fused Drosophila melanogaster tyrosylprotein sulfotransferase, we demonstrated that the activity of TPST determined through MU fluorescence directly correlated with protein sulfation. Kinetic constants obtained with small P-selectin glycoprotein ligand-1 peptide (PSGL-1 peptide, MW 1541) or its large glutathione S-transferase fusion protein (GST-PSGL-1, MW 27833) exhibited significant variation. This assay can be further developed to a high-throughput method for the characterization of TPSTs and for the identification and screening of their protein substrates.

Figure

Fluorophore to report the progress of post-translational protein tyrosine sulfation: Protein sulfation was continuously monitored through a PAPS regeneration system that produced MU (fluorophore) and PAPS (sulfuryl group donor) from MUS and PAP. MU is a fluorescent reporter and PAPS is one of the substrates of TPST.