Differential splicing of the lectin domain of anO-glycosyltransferase modulates both peptide and glycopeptide preferences
Differential splicing of the lectin domain of anO-glycosyltransferase modulates both peptide and glycopeptide preferences
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DOI：
10.1074/jbc.ra120.014700
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发表时间：
2020-08-28
影响因子：
4.8
通讯作者：
Ten Hagen, Kelly G.
中科院分区：
文献类型：
--
作者：
May, Carolyn;Ji, Suena;Ten Hagen, Kelly G.
Mucin-typeO-glycosylation is an essential post-translational modification required for protein secretion, extracellular matrix formation, and organ growth.O-Glycosylation is initiated by a large family of enzymes (GALNTs in mammals and PGANTs inDrosophila) that catalyze the addition of GalNAc onto the hydroxyl groups of serines or threonines in protein substrates. These enzymes contain two functional domains: a catalytic domain and a C-terminal ricin-like lectin domain comprised of three potential GalNAc recognition repeats termed alpha, beta, and gamma. The catalytic domain is responsible for binding donor and acceptor substrates and catalyzing transfer of GalNAc, whereas the lectin domain recognizes more distant extant GalNAc on previously glycosylated substrates. We previously demonstrated a novel role for the alpha repeat of lectin domain in influencing charged peptide preferences. Here, we further interrogate how the differentially spliced alpha repeat of the PGANT9A and PGANT9BO-glycosyltransferases confers distinct preferences for a variety of endogenous substrates. Through biochemical analyses andin silicomodeling using preferred substrates, we find that a combination of charged residues within the alpha repeat and charged residues in the flexible gating loop of the catalytic domain distinctively influence the peptide substrate preferences of each splice variant. Moreover, PGANT9A and PGANT9B also display unique glycopeptide preferences. These data illustrate how changes within the noncatalytic lectin domain can alter the recognition of both peptide and glycopeptide substrates. Overall, our results elucidate a novel mechanism for modulating substrate preferences ofO-glycosyltransferases via alternative splicing within specific subregions of functional domains.
