美國亞利桑那州立大學(xué)生物設(shè)計(jì)研究所的約翰·查普特和他的同事,，將實(shí)驗(yàn)室制造的人工合成蛋白質(zhì)（DX）植入大腸桿菌細(xì)胞,，發(fā)現(xiàn)DX蛋白質(zhì)能與細(xì)胞內(nèi)的ATP分子結(jié)合,，使細(xì)胞分裂停止,，但細(xì)胞仍在繼續(xù)生長,。該研究對(duì)于了解能躲避抗生素的病原體行為提供了新方法,。相關(guān)研究成果刊登在《美國化學(xué)學(xué)會(huì)化學(xué)生物學(xué)》雜志網(wǎng)站上。
“如果你把一個(gè)在試管中創(chuàng)造出來的蛋白質(zhì)植入細(xì)胞內(nèi),，結(jié)果蛋白質(zhì)在細(xì)胞內(nèi)發(fā)生了作用,，”查普特說道，“你覺得細(xì)胞認(rèn)識(shí)它嗎,？細(xì)胞是咀嚼它,，還是把它吐出來？”在這個(gè)值得探索的合成生物學(xué)新領(lǐng)域,，這一發(fā)現(xiàn)將會(huì)使新藥物的研發(fā)取得進(jìn)展,。
“ATP是生命的能量貨幣，”查普特說,，在生物系統(tǒng)的反應(yīng)中,，ATP的磷酸二酯鍵結(jié)合需要一定的能量來驅(qū)動(dòng)。DX蛋白質(zhì)的結(jié)合消耗了細(xì)胞內(nèi)ATP的能量,，破壞了細(xì)胞正常的新陳代謝活動(dòng),，阻止了細(xì)胞分裂，但細(xì)胞們?nèi)栽诶^續(xù)成長,。
大腸桿菌暴露于DX蛋白質(zhì)后,，由通常的球形發(fā)展成細(xì)長的絲狀。在絲狀的細(xì)菌中,，密集的細(xì)胞內(nèi)脂質(zhì)結(jié)構(gòu)被劃分開,，形成了有相同長度的細(xì)胞，研究人員將這種此前未曾出現(xiàn)過的不尋常結(jié)構(gòu)稱為內(nèi)在脂質(zhì)體,。
“這些致密的脂質(zhì)結(jié)構(gòu)正在形成非常有規(guī)律的區(qū)域,，它們沿著絲狀細(xì)胞逐漸形成，它們看起來像是一種防御機(jī)制,，使細(xì)胞自我劃分,。”查普特說道。這一獨(dú)特適應(yīng)過程,，從未在細(xì)菌細(xì)胞中觀察到,，同時(shí)它也是唯一出現(xiàn)在單細(xì)胞有機(jī)體中。合成蛋白質(zhì)DX并不是一件容易事,，它需要精心的模仿自然狀態(tài)下蛋白質(zhì)折疊的特性,，并能夠與關(guān)鍵代謝產(chǎn)物ATP相結(jié)合。
科學(xué)家們接下來將研究,，當(dāng)這些細(xì)胞遇到新情況時(shí),，它們會(huì)如何回應(yīng)。例如細(xì)胞對(duì)于一個(gè)不熟悉的合成蛋白質(zhì),，它們會(huì)如何應(yīng)對(duì),。該研究還指出,，許多傳染性病原體依靠處于休眠狀態(tài)（類似于DX暴露大腸桿菌中觀察到的可生存但不可培養(yǎng)狀態(tài)），躲避抗生素的檢測(cè),。這一發(fā)現(xiàn),，對(duì)于研究這些病原體的行為提供了一個(gè)更好的方法。此外,，對(duì)于生物體極其重要的ATP,，抑制其作用可為防治疾病提供另一種途徑。(生物谷Bioon.com)
DOI: 10.1021/cb3004786
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PMID:
ATP Sequestration by a Synthetic ATP-Binding Protein Leads to Novel Phenotypic Changes in Escherichia coli
Shaleen B. Korch , Joshua M. Stomel †§, Megan A. León †, Matt A. Hamada , Christine R. Stevenson †,Brent W. Simpson †, Sunil K. Gujulla †, and John C. Chaput *†‡
Artificial proteins that bind key metabolites with high affinity and specificity hold great promise as new tools in synthetic biology, but little has been done to create such molecules and examine their effects on living cells. Experiments of this kind have the potential to expand our understanding of cellular systems, as certain phenotypes may be physically realistic but not yet observed in nature. Here, we examine the physiology and morphology of a population of Escherichia coli as they respond to a genetically encoded, non-biological ATP-binding protein. Unlike natural ATP-dependent proteins, which transiently bind ATP during metabolic transformations, the synthetic protein DX depletes the concentration of intracellular ATP and ADP by a mechanism of protein-mediated ligand sequestration. The resulting ATP/ADP imbalance leads to an adaptive response in which a large population of bacilli cells transition to a filamentous state with dense lipid structures that segregate the cells into compartmentalized units. A wide range of biochemical and microscopy techniques extensively characterized these novel lipid structures, which we have termed endoliposomes. We show that endoliposomes adopt well-defined box-like structures that span the full width of the cell but exclude the synthetic protein DX. We further show that prolonged DX exposure causes a large fraction of the population to enter a viable-but-non-culturable state that is not easily reversed. Both phenotypes correlate with strong intracellular changes in ATP and ADP concentration. We suggest that artificial proteins, such as DX, could be used to control and regulate specific targets in metabolic pathways.
