Dp. Mehta et al., UDP-GLCNAC-SER-PROTEIN N-ACETYLGLUCOSAMINE-1-PHOSPHOTRANSFERASE FROM DICTYOSTELIUM-DISCOIDEUM RECOGNIZES SERINE-CONTAINING PEPTIDES AND EUKARYOTIC CYSTEINE PROTEINASES, The Journal of biological chemistry, 272(45), 1997, pp. 28638-28645
Phosphoglycosylation catalyzed by UDP-GlcNAc:Ser-protein N-acetylgluco
samine-1-phosphotransferase (Ser:GlcNAc phosphotransferase) adds GlcNA
c alpha-1-P to peptidyl-Ser of selected Dictyostelium discoideum prote
ins, Lysosomal cysteine proteinase (CP), proteinase-1(CP7), is the maj
or phosphoglycosylated protein in bacterially grown amoebae. GlcNAc-1-
P is added within a Ser-rich domain containing SSS, SGSG, or SGSQ repe
ated motifs that are not found in other papain-like CPs, We studied th
e substrate specificity. of the transferase using peptides containing
these motifs and 12 other peptides with one or more Ser residues, Phos
phoglycosylation is comparable for all three Dictyostelium CP motifs,
but it is not restricted to them, Flanking residues in the other pepti
des strongly influence phosphoglyco, sylation efficiency, Dictyosteliu
m microsomal membranes also phosphoglycosylate endogenous accepters, a
nd some of these accepters occur as an 18 S complex with the transfera
se, CP-serine motif peptides inhibit endogenous acceptor phosphoglycos
ylation weakly (30-40%) at 800 mu M, whereas catalytically inactive pr
oteinase-1(CP7) and other non-phosphoglycosylated eukaryotic CPs, lack
ing the serine domain, inhibit transferase activity at 1-4 mu M. SDS d
enaturation destroys the inhibitory potential of all CPs showing that
transferase recognizes a conformation-dependent feature that is shared
by all, Proteinase-1(CP7) expressed in Escherichia coli lacks GlcNAc-
1-P, but it is a substrate for Ser:GlcNAc phosphotransferase, K-m = 5.
6 mu M. Thus, Ser: GlcNAc phosphotransferase recognizes both acceptor
peptide sequences and a conformational feature of eukaryotic CPs, This
may be physiologically important for establishing or maintaining non-
overlapping groups of GlcNAc-1-P- and Man-6-P-modified Dictyostelium p
roteins that reside in functionally distinct endo-lysosomal vesicles.