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首页> 外文期刊>Journal of Molecular Biology >ALLOSTERIC REGULATION IN A FAMILY OF ENTEROBACTERIAL ASPARTATE TRANSCARBAMYLASES - INTRAMOLECULAR TRANSMISSION OF REGULATORY SIGNALS IN CHIMERIC ENZYMES
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ALLOSTERIC REGULATION IN A FAMILY OF ENTEROBACTERIAL ASPARTATE TRANSCARBAMYLASES - INTRAMOLECULAR TRANSMISSION OF REGULATORY SIGNALS IN CHIMERIC ENZYMES

机译：肠内天冬氨酸转运蛋白家族的异位调节-嵌合酶内调节信号的分子内传递

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Several enterobacterial aspartate transcarbamylases (ATCases) exhibit a [2(c(3)):3(r(2))] quaternary structure analogous to that of the Escherichia coli enzyme. Despite their conserved quaternary structures, these enzymes present substantial differences in the co-operativity of substrate binding and in their allosteric regulation by nucleotide effecters. A comparison between different enzymatic species provides an opportunity to expand our understanding of the molecular basis of allostery in ATCase. Chimeric ATCases were constructed by exchanging subdomain regions involved in quaternary structural features, such as the r1-c4 regulatory-catalytic subunit interface analyzed in this study, in order to define the involvement of this interface in the several components of allosteric regulation. The r1-c4 interface was found to constitute an essential element for the recognition and the transmission of the ATP regulatory signal in the Serratia marcescens and the Proteus vulgaris ATCases, as it does in the E. coli ATCase. Besides, the specific amino acid composition of the C-terminal region of the regulatory chain and its interactions with the amino acid residues in the 240s loop of the catalytic chain (r1-c4 interactions) were found to modulate the amplitude of the enzyme's response to ATP. The C-terminal region of the regulatory chain did not appear to participate directly in the regulation of the three native ATCases by CTP. Even when CTP acts as an activator, as in the P. vulgaris and S. marcescens ATCases, its signal follows a route distinct from that of the general activator ATP. Synergistic inhibition by CTP and UTP was found to involve the transmission of a specific UTP signal. This signal appeared different in the various ATCases, involving the C-terminal region of the regulatory chain in the E. coli and S. marcescens ATCases but not in the P. vulgaris ATCase. (C) 1996 Academic Press Limited [References: 36]
机译：几种肠细菌天冬氨酸转氨酶（ATCases）具有类似于大肠杆菌酶的[2（c（3））：3（r（2））]四级结构。尽管它们具有保守的四级结构，但这些酶在底物结合的协同操作性和核苷酸效应物的变构调节方面都存在实质性差异。不同酶物种之间的比较提供了一个机会，可以扩展我们对ATCase变构分子基础的理解。通过交换涉及四级结构特征的子域区域（例如本研究中分析的r1-c4调控催化亚基界面）来构建嵌合ATCases，以定义该界面在变构调控的几个组成部分中的参与。发现r1-c4界面与粘质沙雷氏菌和寻常变形杆菌ATCases中的ATP调节信号的识别和传递一样，就像在大肠杆菌ATCase中一样，也是必不可少的元素。此外，发现调节链C端区域的特定氨基酸组成及其与催化链240s环中氨基酸残基的相互作用（r1-c4相互作用）可调节酶对以下酶的响应幅度ATP。调节链的C末端区域似乎没有直接参与CTP对三种天然ATCases的调节。甚至当CTP充当激活剂时，例如在寻常性假单胞菌和marcescens ATCases中，其信号所遵循的路径也不同于一般激活剂ATP。发现通过CTP和UTP的协同抑制作用涉及特定UTP信号的传输。该信号在各种ATCases中似乎有所不同，涉及大肠杆菌和marcescens ATCases中调控链的C端区域，而在寻常型假单胞菌ATCase中则没有。 （C）1996 Academic Press Limited [参考：36]

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