1O23

CRYSTAL STRUCTURE OF LACTOSE SYNTHASE IN THE PRESENCE OF UDP-GLUCOSE

「1NT7」から置き換えられました 「1JNC」から置き換えられました

1O23 の概要

• エントリーDOI: 10.2210/pdb1o23/pdb
• 分子名称: ALPHA-LACTALBUMIN, BETA-1,4-GALACTOSYLTRANSFERASE, CALCIUM ION, ... (9 entities in total)
• 機能のキーワード: alpha-lactalbumin; beta, 1, 4-galactosyltransferase; udp-glucose, transferase activator-transferase complex, transferase activator/transferase
• 由来する生物種: Mus musculus (house mouse); 詳細
• 細胞内の位置: Secreted: P29752; Isoform Long: Golgi apparatus, Golgi stack membrane; Single-pass type II membrane protein. Isoform Short: Golgi apparatus, Golgi stack membrane; Single-pass type II membrane protein. Processed beta-1,4-galactosyltransferase 1: Secreted: P08037
• タンパク質・核酸の鎖数: 4
• 化学式量合計: 96449.55

構造登録者

Ramakrishnan, B.,Shah, P.S.,Qasba, P.K. (登録日: 2003-01-29, 公開日: 2003-02-25, 最終更新日: 2023-12-27)

主引用文献

Ramakrishnan, B.,Shah, P.S.,Qasba, P.K.
Alpha-Lactalbumin (La) Stimulates Milk Beta-1,4-Galactosyltransferase I (Beta 4Gal-T1) to Transfer Glucose from Udp-Glucose to N-Acetylglucosamine. Crystal Structure of Beta 4Gal-T1 X La Complex with Udp-Glc.
J.Biol.Chem., 276:37665-37671, 2001

PubMed Abstract: beta-1,4-Galactosyltransferase 1 (Gal-T1) transfers galactose (Gal) from UDP-Gal to N-acetylglucosamine (GlcNAc), which constitutes its normal galactosyltransferase (Gal-T) activity. In the presence of alpha-lactalbumin (LA), it transfers Gal to Glc, which is its lactose synthase (LS) activity. It also transfers glucose (Glc) from UDP-Glc to GlcNAc, constituting the glucosyltransferase (Glc-T) activity, albeit at an efficiency of only 0.3-0.4% of Gal-T activity. In the present study, we show that LA increases this activity almost 30-fold. It also enhances the Glc-T activity toward various N-acyl substituted glucosamine acceptors. Steady state kinetic studies of Glc-T reaction show that the K(m) for the donor and acceptor substrates are high in the absence of LA. In the presence of LA, the K(m) for the acceptor substrate is reduced 30-fold, whereas for UDP-Glc it is reduced only 5-fold. In order to understand this property, we have determined the crystal structures of the Gal-T1.LA complex with UDP-Glc x Mn(2+) and with N-butanoyl-glucosamine (N-butanoyl-GlcN), a preferred sugar acceptor in the Glc-T activity. The crystal structures reveal that although the binding of UDP-Glc is quite similar to UDP-Gal, there are few significant differences observed in the hydrogen bonding interactions between UDP-Glc and Gal-T1. Based on the present kinetic and crystal structural studies, a possible explanation for the role of LA in the Glc-T activity has been proposed.

PubMed: 11485999
DOI: 10.1074/jbc.M102458200

実験手法

X-RAY DIFFRACTION (2.32 Å)