Abstract
We have identified the site of tyrosine sulfation in an insect secretory protein, yolk protein 2 of Drosophila melanogaster. Yolk proteins were purified from [35S]sulfate-labeled flies, and yolk protein 2 was separated from yolk protein 1 and yolk protein 3 by preparative two-dimensional polyacrylamide gel electrophoresis. After digestion of yolk protein 2 with trypsin and reversed-phase high performance liquid chromatography, the sulfate label was recovered in two distinct sulfopeptides which, however, had identical NH2-terminal sequences and contained 3 tyrosine residues each. After chymotryptic digestion of the two tryptic sulfopeptides, the sulfate label was recovered in one sulfopeptide which contained a single tyrosine residue. NH2-terminal sequencing showed that this tyrosine residue corresponded to tyrosine 172 of the yolk protein 2 precursor (Hung, M.-C., and Wensink, P. C. (1983) J. Mol. Biol. 164, 487-492) in the sequence Glu-Thr-Thr-Asp-Tyr(S)-Ser-Asn-Glu-Glu. This insect tyrosine sulfation site is very similar to the known vertebrate tyrosine sulfation sites in terms of amino acid composition and secondary structure. In the accompanying paper (Friederich, E., Baeuerle, P. A., Garoff, H., Hovemann, B., and Huttner, W. B. (1988) J. Biol. Chem. 263, 14930-14938), we report on the expression of Drosophila yolk protein 2 in mouse fibroblasts and show the in vivo sulfation of tyrosine 172 by the vertebrate tyrosylprotein sulfotransferase.
