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首页> 外文期刊>Acta crystallographica.Section D. Biological crystallography >Participation of Cys123 of Escherichia coli succinyl-CoA synthetase in catalysis
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Participation of Cys123 of Escherichia coli succinyl-CoA synthetase in catalysis

机译：参与Cys123大肠杆菌琥珀酰辅酶合成酶的催化

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摘要

Succinyl-CoA synthetase has a highly conserved cysteine residue, Cys123 in the Escherichia coli enzyme, that is located near the CoA-binding site and the active-site histidine residue. To test whether the succinyl moiety of succinyl-CoA is transferred to the thiol of Cys123 as part of the catalytic mechanism, this residue was mutated to alanine, serine, threonine and valine. Each mutant protein was catalytically active, although less active than the wild type. This proved that the specific formation of a thioester bond with Cys123 is not part of the catalytic mechanism. To understand why the mutations affected catalysis, the crystal structures of the four mutant proteins were determined. The alanine mutant showed no structural changes yet had reduced activity, suggesting that the size of the cysteine is important for optimal activity. These results explain why this cysteine residue is conserved in the sequences of succinyl-CoA synthetases from different sources.
机译：琥珀酰辅酶合成酶具有高度保守的半胱氨酸残基,Cys123大肠杆菌酶,这是附近CoA-binding站点和活性部位组氨酸残基。是否琥珀酰琥珀酰辅酶的一部分转移到Cys123的硫醇的一部分催化机理,这渣是突变丙氨酸、丝氨酸、苏氨酸和缬氨酸。突变蛋白催化地活跃,虽然比野生型不活跃。特定的硫酯键的形成Cys123不是催化机理的一部分。理解为什么突变影响催化,四个突变体的晶体结构蛋白质测定。显示没有结构性变化已减少活动,建议的大小半胱氨酸对最优活动很重要。结果解释为什么这个半胱氨酸残基保存在琥珀酰辅酶的序列从不同的来源合成酶。

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