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首页> 外文期刊>Journal of Molecular Biology >STRUCTURAL ORGANIZATION AND ASSEMBLY OF FLAGELLAR HOOK PROTEIN FROM SALMONELLA TYPHIMURIUM
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STRUCTURAL ORGANIZATION AND ASSEMBLY OF FLAGELLAR HOOK PROTEIN FROM SALMONELLA TYPHIMURIUM

机译：鼠伤寒沙门氏菌腓肠钩蛋白的结构组织与组装

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The terminal regions of monomeric hook protein from Salmonella typhimurium are known to be highly mobile and exposed to the solvent. Although hook protein exhibits an unusual far-UV circular dichroism spectrum, resembling that of random coil structures, our calorimetric experiments clearly demonstrate that the molecule has a compact ordered core. The compact part probably consists of three domains as suggested by deconvolution analysis of the calorimetric melting profiles. Secondary structure prediction, together with the analysis of far-UV circular dichroism spectra, has shown that the domains of monomeric hook protein contain beta-sheeted structures without significant alpha-helical content. The polymerization of hook protein is accompanied by the stabilization of its disordered terminal regions into a predominantly alpha-helical domain. Evaluation of circular dichroism data suggests that about 45 terminal residues are involved in helical segments. Coiled-coil prediction indicates that whereas the whole carboxy-terminal helical region of hook protein has a strong bundle-forming potential, there is only a single short amino-terminal segment exhibiting weak coiled-coil forming tendencies. The formation of alpha-helical bundles is commonly believed to be a key event during the polymerization of the axial structure of bacterial flagella. To clarify the role of helical bundle formation in hook assembly proteolytic fragments of hook protein with truncations of various lengths in their carboxy-terminal disordered regions were generated, and their polymerizational behavior was investigated. We found that even fragments completely lacking the main helix-forming carboxy-terminal regions can polymerize into filaments in vitro under appropriately high salt concentrations. Our results suggest that, although helical bundle formation may occur during self-assembly, governing precise subunit packing and playing an important role in the stabilization of hook filaments, it is not the principal interaction mainly responsible for the development of their filamentous structure. (C) 1995 Academic Press Limited [References: 41]
机译：鼠伤寒沙门氏菌的单体钩蛋白的末端区域已知是高度可移动的并且暴露于溶剂中。尽管钩蛋白表现出不寻常的远紫外圆二色性光谱，类似于随机线圈结构，但我们的量热实验清楚地表明该分子具有紧密的有序核。压缩量曲线的反卷积分析表明，紧凑部分可能包括三个域。二级结构预测以及对远紫外圆二色性光谱的分析表明，单体钩蛋白的结构域包含β-折叠的结构，而没有明显的α-螺旋含量。钩蛋白的聚合反应伴随着其无序末端区域稳定为主要为α螺旋结构域。圆二色性数据的评估表明，螺旋段中约有45个末端残基。卷曲螺旋预测表明，尽管钩蛋白的整个羧基末端螺旋区域具有很强的成束潜力，但只有一个短的氨基末端片段显示出弱的卷曲螺旋形成趋势。通常认为，α-螺旋束的形成是细菌鞭毛轴向结构聚合过程中的关键事件。为了阐明螺旋束形成在钩组装中的钩蛋白的蛋白水解片段中的作用，在其羧基末端无序区域中截短了各种长度，并研究了它们的聚合行为。我们发现，即使完全缺乏主要螺旋形成羧基末端区域的片段，也可以在适当高盐浓度下在体外聚合成细丝。我们的结果表明，尽管螺旋束的形成可能在自组装过程中发生，控制着精确的亚基堆积，并在钩丝的稳定化中起着重要作用，但它并不是主要的相互作用，主要是其丝状结构的发展。 （C）1995 Academic Press Limited [参考号：41]

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