PDF(Pubmed)
Abstract：
N-acetylgalactosaminyl-transferases (GalNAc-Ts) initiate mucin-type O-glycosylation, an abundant and complex posttranslational modification that regulates host-microbe interactions, tissue development, and metabolism. GalNAc-Ts contain a lectin domain consisting of three homologous repeats (α, β, and γ), where α and β can potentially interact with O-GalNAc on substrates to enhance activity toward a nearby acceptor Thr/Ser. The ubiquitous isoenzyme GalNAc-T1 modulates heart development, immunity, and SARS-CoV-2 infectivity, but its substrates are largely unknown. Here, we show that both α and β in GalNAc-T1 uniquely orchestrate the O-glycosylation of various glycopeptide substrates. The α repeat directs O-glycosylation to acceptor sites carboxyl-terminal to an existing GalNAc, while the β repeat directs O-glycosylation to amino-terminal sites. In addition, GalNAc-T1 incorporates α and β into various substrate binding modes to cooperatively increase the specificity toward an acceptor site located between two existing O-glycans. Our studies highlight a unique mechanism by which dual lectin repeats expand substrate specificity and provide crucial information for identifying the biological substrates of GalNAc-T1.
摘要：
N-乙酰半乳糖胺基转移酶（GalNAc-Ts）启动粘蛋白型O-糖基化，丰富而复杂的翻译后修饰，调节宿主-微生物相互作用，组织发育，和新陈代谢。GalNAc-Ts包含一个由三个同源重复序列组成的凝集素结构域（α，β,和γ)，其中α和β可以潜在地与底物上的O-GalNAc相互作用以增强对附近受体Thr/Ser的活性。普遍存在的同工酶GalNAc-T1调节心脏发育，豁免权,和SARS-CoV-2传染性，但是它的底物在很大程度上是未知的。这里,我们表明GalNAc-T1中的α和β都独特地协调了各种糖肽底物的O-糖基化。α重复将O-糖基化引导到现有GalNAc的羧基末端的受体位点，而β重复将O-糖基化引导到氨基末端位点。此外,GalNAc-T1将α和β结合到各种底物结合模式中,以协同地增加对位于两个现有O-聚糖之间的受体位点的特异性。我们的研究强调了一种独特的机制，通过该机制，双重凝集素重复扩展了底物特异性，并为鉴定GalNAc-T1的生物底物提供了关键信息。
