Title : Identification of amino acids that modulate
mannose phosphorylation of mouse
DNase I , a secretory
glycoprotein
Abstract :
- We have reported that bovine DNase I , a secretory glycoprotein , acquires mannose 6-phosphate residues on 12.6% of its Asn-linked oligosaccharides Asn-linked oligosaccharides when expressed in COS-1 cells and that the extent of phosphorylation increases to 79.2% when lysines are placed at positions 27 and 74 of the mature protein (Nishikawa, A., Gregory, W. , Frenz, J., Cacia, J., and Kornfeld, S. (1997) J. Biol
- Chem
- 272, 19408-19412)
- We now demonstrate that murine DNase I , which contains Lys27 and Lys74 , is phosphorylated only 20.9% when expressed in the same COS-1 cell system
- This difference is mostly due to the absence of three residues present in bovine DNase I ( Tyr54, Lys124, and Ser190 ) along with the presence of a valine at position 23 that is absent in the bovine species
- We show that Val23 inhibits phosphorylation at the Asn18 glycosylation site , whereas Tyr54, Lys124, and Ser190 enhance phosphorylation at the Asn106 glycosylation site
- Tyr54 and Ser190 are widely separated from each other and from Asn106 on the surface of DNase I , indicating that residues present over a broad area influence the interaction with UDP-GlcNAc:lysosomal enzyme N-acetylglucosamine-1-phosphotransferase , which is responsible for the formation of mannose 6-phosphate residues on lysosomal enzymes