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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >A cluster of basic amino acids within an alpha-helix is essential for alpha-subunit recognition by the glycoprotein hormone N-acetylgalactosaminyltransferase.
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A cluster of basic amino acids within an alpha-helix is essential for alpha-subunit recognition by the glycoprotein hormone N-acetylgalactosaminyltransferase.

机译：α螺旋中的碱性氨基酸簇对于糖蛋白激素N-乙酰半乳糖胺基转移酶的α亚基识别至关重要。

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摘要

The glycoprotein hormone N-acetylgalactosaminyltransferase is responsible for synthesis of Asn-linked oligosaccharides terminating with GalNAc-4-SO4 on lutropin, thyrotropin, and the uncombined glycoprotein hormone alpha subunit. We previously established that a recognition determinant for the N-acetylgalactosaminyltransferase is contained within a 22-amino acid glycopeptide fragment of the alpha subunit. We proposed that the tripeptide Pro-Leu-Arg is an essential element of the recognition determinant. Using site-directed mutagenesis we have examined the role of individual amino acids in recognition by the glycoprotein hormone N-acetylgalactosaminyltransferase. Within the sequence Pro40-Leu41-Arg42-Ser43-Lys44-Lys45, Lys44, and Lys45, as well as Arg42 of the tripeptide, are essential for recognition. Substitution of the Leu41 with other amino acids can either increase or decrease the rate of GalNAc transfer over an 8-fold range, suggesting that the middle amino acid of the tripeptide plays a modulatory role in recognition. The critical Leu41-Arg42 and Lys44-Lys45 residues are present on the same surface of an alpha-helix, which projects from the surface of the alpha subunit. Our results indicate that an essential element of the recognition determinant consists of a cluster of basic residues and that neutral but not negatively charged residues are tolerated within this cluster.
机译：糖蛋白激素N-乙酰半乳糖胺基转移酶负责合成在Lutropin，促甲状腺素和未结合的糖蛋白激素α亚基上终止于GalNAc-4-SO4的Asn连接的寡糖。我们先前确定，α-亚基的22个氨基酸的糖肽片段中包含N-乙酰半乳糖胺基转移酶的识别决定簇。我们提出三肽Pro-Leu-Arg是识别决定簇的基本要素。使用定点诱变，我们检查了单个氨基酸在糖蛋白激素N-乙酰半乳糖胺基转移酶识别中的作用。在序列Pro40-Leu41-Arg42-Ser43-Lys44-Lys45，Lys44和Lys45以及三肽的Arg42内，对于识别是必不可少的。用其他氨基酸取代Leu41可以在8倍范围内提高或降低GalNAc转移的速率，这表明三肽的中间氨基酸在识别中起调节作用。关键的Leu41-Arg42和Lys44-Lys45残基存在于从α亚基表面突出的α螺旋的同一表面上。我们的结果表明，识别决定簇的基本元素由一组基本残基组成，并且在该群集中可以容忍中性但无负电荷的残基。

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