Existence of distinct tyrosylprotein sulfotransferase genes: Molecular characterization of tyrosylprotein sulfotransferase-2

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Abstract
Tyrosylprotein sulfotransferase (TPST) is a 54- to 50-kDa integral membrane glycoprotein of the trans-Golgi network found in essentially all tissues investigated, catalyzing the tyrosine O-sulfation of soluble and membrane proteins passing through this compartment. Here we describe ( i ) an approach to identify the TPST protein, referred to as MSC ( m odification after s ubstrate c rosslinking) labeling, which is based on the crosslinking of a substrate peptide to TPST followed by intramolecular [ 35 S]sulfate transfer from the cosubstrate 3′-phosphoadenosine 5′-phosphosulfate (PAPS); and ( ii ) the molecular characterization of a human TPST, referred to as TPST-2, whose sequence is distinct from that reported [TPST-1; Ouyang, Y.-B., Lane, W. S. & Moore, K. L. (1998) Proc. Natl. Acad. Sci. USA 95, 2896–2901] while this study was in progress. Human TPST-2 is a type II transmembrane protein of 377 aa residues that is encoded by a ubiquitously expressed 1.9-kb mRNA originating from seven exons of a gene located on chromosome 22 (22q12.1). A 304-residue segment in the luminal domain of TPST-2 shows 75% amino acid identity to the corresponding segment of TPST-1, including conservation of the residues implicated in the binding of PAPS. Expression of the TPST-2 cDNA in CHO cells resulted in an ≈13-fold increase in both TPST protein, as determined by MSC labeling, and TPST activity. A predicted 359-residue type II transmembrane protein in Caenorhabditis elegans with 45% amino acid identity to TPST-2 in a 257-residue segment of the luminal domain points to the evolutionary conservation of the TPST protein family.