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首页> 外文期刊>Journal of Molecular Biology >Proximal regions of the catalytic gamma and regulatory beta subunits on the interior lobe face of phosphorylase kinase are structurally coupled to each other and with enzyme activation
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Proximal regions of the catalytic gamma and regulatory beta subunits on the interior lobe face of phosphorylase kinase are structurally coupled to each other and with enzyme activation

机译：磷酸化酶激酶的内叶面上的催化性γ和调节性β亚基的近端区域在结构上彼此偶联并且具有酶活化

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摘要

Phosphorylase kinase from skeletal muscle is a hexadecameric enzyme with the subunit composition (alphabeta gammadelta)4 and a mass of 1.3 x 10(6) Da. The catalytic gamma subunit and the remaining regulatory subunits are packed as a tetrahedral structure composed of two elongated, opposing (alphabeta gammadelta)2 octameric lobes. We show by immunoelectron microscopy with subunit-specific monoclonal antibodies that a portion of the beta subunit occurs on the interior face of the lobes at a region of inter-lobal interactions, and that at a proximal position slightly more central and distal on the interior lobe face lies the base (residues 277 to 290) of the helical domain of the catalytic core of the gamma subunit. Activation of the kinase by a variety of means caused similar increases in the binding to the holoenzyme of the monoclonal antibodies against these two regions of the beta and gamma subunits. Moreover, monovalent fragments of the antibodies against both regions stimulated the activity of the non-activated holoenzyme. Thus, the epitopes of the beta and gamma subunits recognized by the monoclonal antibodies are structurally coupled to each other and with the activation of phosphorylase kinase. Activation of the holoenzyme apparently involves the repositioning of the base of the catalytic domain of the gamma subunit and a proximal region of the beta subunit within the identified area on the interior face of the lobes of the tetrahedral phosphorylase kinase molecule.
机译：来自骨骼肌的磷酸化酶激酶是一种十六聚酶，其亚基组成为（alphabeta gammadelta）4，质量为1.3 x 10（6）Da。催化γ亚基和其余的调节亚基包装成由两个细长的相对的（αbetagammadelta）2八聚体叶组成的四面体结构。我们用亚基特异的单克隆抗体通过免疫电子显微镜观察到，一部分β亚基出现在叶间相互作用区域的叶的内表面上，并且在近端位置更靠近内叶中心和远端面位于γ亚基催化核心螺旋结构域的基部（残基277至290）。通过多种手段激活激酶会导致针对β和γ亚基这两个区域的单克隆抗体与全酶的结合性相似增加。而且，针对两个区域的抗体的单价片段刺激了未活化的全酶的活性。因此，被单克隆抗体识别的β和γ亚基的表位在结构上彼此偶联并且与磷酸化酶激酶激活。全酶的活化显然涉及到在四面体磷酸化酶激酶分子的内表面的确定区域内，γ亚基的催化结构域的碱基和β亚基的近端区域的重新定位。

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