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首页> 外文期刊>Acta crystallographica.Section D Biological crystallography. >Structure of the epimerization domain of tyrocidine synthetase A
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Structure of the epimerization domain of tyrocidine synthetase A

机译：差向异构化作用的结构域短杆菌酪肽合成酶的

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摘要

Tyrocidine, a macrocyclic decapeptide from Bacillus brevis, is nonribosomally assembled by a set of multimodular peptide synthetases, which condense two d-amino acids and eight l-amino acids to produce this membrane-disturbing antibiotic. d-Phenylalanine, the first amino acid incorporated into tyrocidine, is catalytically derived from enzyme-bound l-Phe by the C-terminal epimerization (E) domain of tyrocidine synthetase A (TycA). The 1.5? resolution structure of the cofactor-independent TycA E domain reveals an intimate relationship to the condensation (C) domains of peptide synthetases. In contrast to the latter, the TycA E domain uses an enlarged bridge region to plug the active-site canyon from the acceptor side, whereas at the donor side a latch-like floor loop is suitably extended to accommodate the III helix of the preceding peptide-carrier domain. Additionally, E domains exclusively harbour a conserved glutamate residue, Glu882, that is opposite the active-site residue His743. This active-site topology implies Glu882 as a candidate acid-base catalyst, whereas His743 stabilizes in the protonated state a transient enolate intermediate of the l?d isomerization.
机译：短杆菌酪肽,大环的十肽短杆菌,nonribosomally组装的组multimodular肽合成酶,两个分子酸和八l-amino浓缩而成这个membrane-disturbing酸生产抗生素。纳入短杆菌酪肽,是催化地来自enzyme-bound l-Phe c端差向异构化作用(E)短杆菌酪肽合成酶的领域(TycA)。cofactor-independent TycA E领域展现了一个亲密关系的冷凝(C)域的肽合成酶。后者,TycA E域使用一个放大桥塞的活性部位峡谷地区受体的一面,而在捐赠方面latch-like地板循环适当扩展容纳三螺旋的前面peptide-carrier域。只含有一种守恒的谷氨酸Glu882残留,对活性部位His743残留。Glu882作为候选人酸碱催化剂,而His743稳定使质子化状态瞬态l的烯醇化物中间?异构化。

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