Sequences Prior to Conserved Catalytic Motifs of Polysialyltransferase ST8Sia IV Are Required for Substrate Recognition

Abstract

Background:The polysialyltransferase, polysialylate, selects a group of proteins. Results: Substrate recognition and polysialylation are reduced when basic residues in a noncatalytic region of ST8SiaIV/PST are replaced. Conclusion: Specific residues in a polysialyltransferase polybasic region are critical for substrate recognition. Significance: Understanding the mechanism of protein-specific polysialylation will allow for the modulation of this process during development and disease.

Novel Regulation of Skp1 by the Dictyostelium AgtA α-Galactosyltransferase Involves the Skp1-binding Activity of Its WD40 Repeat Domain

“…Mass Spectrometry of AgtA Reaction Products-Reactions containing Fuc-pNP, FG-octyl, and FGGn-pNP were carried to near completion, adsorbed to a SepPak C 18 , eluted in MeOH, dried, and analyzed by MALDI-TOF-MS on a Bruker Ultraflex II, in positive ion mode using dihydroxybenzoic acid as the matrix (19).…”

“…Although the WD40 repeats of AgtA are unprecedented for known GTs, other GTs possess SH3 (14), TPR (15), and lectin (16) domains. In some instances, these so-called "add-on" domains (17) have been implicated in acceptor substrate recognition, as has the linker region of a type 2 membrane GT (18). Thus the AgtA C-terminal domain may contribute to Skp1 recognition, although it is noted that the earlier GTs in the pathway, the ␣GlcNAcT (Gnt1) and PgtA (see Fig.…”

Structure of human ST8SiaIII sialyltransferase provides insight into cell-surface polysialylation

“…Bioinformatic analyses of ST8SiaII and ST8SiaIV predicted, in addition to the conserved sialylmotifs, two additional polysialyltransferasespecific motifs, termed the polysialyltransferase domain (PSTD; a stretch of 32 amino acids immediately upstream of sialylmotif SML) and the polybasic region (PBR; a stretch of 34 residues at the N terminus of the catalytic domain) 13,49 (Fig. 4a and Supplementary Fig.…”

“…deviation (Å) whereas the PBR is crucial for proteinspecific polysialylation 13,49 and has been suggested to function in recognition of the acidic patch in the first FN1 repeat of NCAM.…”

The Polysialyltransferases Interact with Sequences in Two Domains of the Neural Cell Adhesion Molecule to Allow Its Polysialylation

“…Interestingly, results from our laboratory suggest that residues in a polybasic region at the polyST stem-catalytic domain border are likely to be involved in the initial FN1 recognition event (47,48). In the case of OCAM, the presence of large basic residues and other non-conserved sequences in Ig5 decrease or block the secondary contacts with the Ig5 domain that are essential for the proper positioning of the enzyme and polysialylation.…”