三维结构的galactose-1-phosphate uridylyltransferase从大肠杆菌1.8决议。
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弗雷·韦德金德我,PA, Rayment我
三维结构的galactose-1-phosphate uridylyltransferase从大肠杆菌1.8决议。
生物化学。1995年9月5日,34 (35):11049 - 61。
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7669762 (在PubMed]
- 文摘
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Galactose-1-phosphate uridylyltransferase催化的可逆转移尿苷5 ' -monophosphoryl一半的UDP-glucose的磷酸基半乳糖1-phosphate UDP-galactose。这种酶参与Leloir半乳糖代谢途径,及其缺乏的主要原因是半乳糖血症可能致命的疾病。从大肠杆菌二聚的酶的三维结构包裹着尿苷5 '磷酸氢盐报告在这里。由多个同形结构解决了更换和电子密度改性技术,精制1.8解决方案。酶亚基包含单个域的拓扑“half-barrel”。楼板是由九股反平行的β褶板。桶轴大约是平行于当地二分体,每个亚基有关。两两亲的螺旋线填补half-barrel封存其疏水室内。一个铁原子位于桶的外面,集中在亚基接口。Intrasubunit协调铁像扭曲的广场金字塔由两个组氨酸和双齿羧酸盐的赤道结扎组和一个轴向组氨酸。 The subunit interface is stabilized by this coordination and is further characterized by the formation of two intermolecular "mini-sheets" distinct from the strands of the half-barrel. Loops that connect the mini-sheet strands contribute to the formation of the active site, which resides on the external surface of the barrel rim. Loops of the barrel strands are tethered together by a structural zinc atom that orients the local fold in a manner essential for catalysis. In one of the latter loops, S gamma of a cysteine is modified by beta-mercaptoethanol, which prevents the alpha-phosphorus of the nucleotide from access to the nucleophile His166. This conformation does not appear to perturb the interactions to the uracil and ribose moieties as mediated through the side chains of Leu54, Ohe75, Asn77, Asp78, Phe79, and Val108. Several of the latter residues have been implicated in human galactosemia. The present structure explains the deleterious effects of many of those mutations.