Interaction of serine acetyltransferase with O-acetylserine sulfhydrylase active site:: Evidence from fluorescence spectroscopy
Interaction of serine acetyltransferase with O-acetylserine sulfhydrylase active site:: Evidence from fluorescence spectroscopy
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DOI：
10.1110/ps.051492805
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发表时间：
2005-08-01
期刊：
影响因子：
8
通讯作者：
Mozzarelli, A
中科院分区：
文献类型：
--
作者：
Campanini, B;Speroni, F;Mozzarelli, A
丝氨酸乙酰转移酶是细菌和植物硫同化途径的关键酶，已知与半胱氨酸生物合成途径的最后一个酶o -乙酰丝氨酸巯基化酶形成双酶复合物。复合物的生物学功能和组成酶的相互调节机制仍然知之甚少。在这项工作中，利用5'-磷酸吡哆醛对辅助因子微环境和蛋白质基质内构象变化敏感的荧光特性，研究了络合物形成对o-乙酰丝氨酸巯基水解酶活性位点的影响。结果表明，丝氨酸乙酰化转移酶及其c端十肽均与o -乙酰丝氨酸巯基酶的（x-羧基）亚基结合，引发从开放到封闭的构象转变。这一发现表明，丝氨酸乙酰转移酶可以通过双重机制抑制o -乙酰丝氨酸巯基水解酶的催化活性，即与o -乙酰丝氨酸竞争与酶活性位点的结合，以及稳定天然底物难以接近的封闭构象。
Serine acetyltransferase is a key enzyme in the sulfur assimilation pathway of bacteria and plants, and is known to form a bienzyme complex with O-acetylserine sulfhydrylase, the last enzyme in the cysteine biosynthetic pathway. The biological function of the complex and the mechanism of reciprocal regulation of the constituent enzymes are still poorly understood. In this work the effect of complex formation on the O-acetylserine sulfhydrylase active site has been investigated exploiting the fluorescence properties of pyridoxal 5'-phosphate, which are sensitive to the cofactor micro-environment and to conformational changes within the protein matrix. The results indicate that both serine acetyltransferase and its C-terminal decapeptide bind to the (x-carboxyl subsite of O-acetylserine sulfhydrylase, triggering a transition from an open to a closed conformation. This finding suggests that serine acetyltransferase can inhibit O-acetylserine sulfhydrylase catalytic activity with a double mechanism, the competition with O-acetylserine for binding to the enzyme active site and the stabilization of a closed conformation that is less accessible to the natural substrate.