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首页> 外文期刊>Journal of Molecular Biology >Cotranslational Folding of a Pentarepeat beta-Helix Protein
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Cotranslational Folding of a Pentarepeat beta-Helix Protein

机译：双抗疟疾β-螺旋蛋白的键入折叠

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It is becoming increasingly clear that many proteins start to fold cotranslationally before the entire polypeptide chain has been synthesized on the ribosome. One class of proteins that a priori would seem particularly prone to cotranslational folding is repeat proteins, that is, proteins that are built from an array of nearly identical sequence repeats. However, while the folding of repeat proteins has been studied extensively in vitro with purified proteins, only a handful of studies have addressed the issue of cotranslational folding of repeat proteins. Here, we have determined the structure and studied the cotranslational folding of a beta-helix pentarepeat protein from the human pathogen Clostridium botulinum a homolog of the fluoroquinolone resistance protein MfpA-using an assay in which the SecM translational arrest peptide serves as a force sensor to detect folding events. We find that cotranslational folding of a segment corresponding to the first four of the eight beta-helix coils in the protein produces enough force to release ribosome stalling and that folding starts when this unit is similar to 35 residues away from the P-site, near the distal end of the ribosome exit tunnel. An additional folding transition is seen when the whole PENT moiety emerges from the exit tunnel. The early cotranslational formation of a folded unit may be important to avoid misfolding events in vivo and may reflect the minimal size of a stable beta-helix since it is structurally homologous to the smallest known beta-helix protein, a four-coil protein that is stable in solution. (C) 2018 Elsevier Ltd. All rights reserved.
机译：它正变得越来越清楚的是许多蛋白质开始共翻译折叠整个多肽链已经在核糖体上被合成之前。一类蛋白，其先验似乎特别容易发生共翻译折叠的是重复蛋白，即，从它们的几乎相同的重复序列的阵列构建的蛋白质。然而，虽然重复蛋白的折叠已经与纯化的蛋白质广泛体外研究，只有研究了一把已经解决了重复蛋白共翻译折叠的问题。这里，我们已经确定的结构和从所述人病原体肉毒梭菌MFPA-使用化验，其中SECM平移逮捕肽用作力传感器氟喹诺酮抗性蛋白质的同源物研究β-螺旋的共翻译折叠pentarepeat蛋白检测折叠事件。我们发现对应于蛋白质的八个测试螺旋线圈的前四个段的该共翻译折叠产生足够的力量来释放核糖体失速和折叠开始时，这个单位是类似于35个残基从P-现场移走，附近核糖体隧道出口的远端。当整个PENT部分从出口隧道出现一个附加的折叠过渡能够被看见。折叠单元的早期共翻译的形成可能是重要的，以避免错误折叠体内事件和可能反映了稳定的β-螺旋的最小尺寸，因为它在结构上同源的已知的最小的β-螺旋蛋白，四线圈蛋白质即在溶液中稳定。 （c）2018年elestvier有限公司保留所有权利。

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