2013年6月30日 訊 /生物谷BIOON/ --近日一項刊登在國際雜志Molecular Microbiology上的研究報告中，來自馬薩諸塞大學(xué)的研究者通過使用生化技術(shù)和質(zhì)譜分析法來追蹤蛋白酶ClpXP,，從而揭示蛋白質(zhì)的降解對于細胞周期進程以及細菌的發(fā)育重要的分子機制,，這項研究或為開發(fā)新型抗生素提供思路。
研究者表示,，在細菌細胞中,，蛋白質(zhì)的降解對于其生長發(fā)育以及適應(yīng)環(huán)境都至關(guān)重要。一種名為能量依賴性的蛋白酶類對于主要來負責(zé)細菌細胞蛋白質(zhì)的降解,，但是這些蛋白酶識別什么樣的靶點以及如何工作目前并不清楚,。
這項研究中，研究者使用模式細菌新月柄桿菌來進行研究,，首先研究者構(gòu)建了蛋白酶突變體,，這樣突變體細菌細胞就不能識別下游靶點，隨后研究者就利用質(zhì)譜分析法來識別被捕獲的蛋白質(zhì),，這些靶點蛋白包括了參與細菌DNA復(fù)制,、轉(zhuǎn)錄以及細胞骨架改變等過程的蛋白質(zhì)。
下一步研究者篩選到了一種名為TacA的蛋白質(zhì)，新月柄桿菌每分裂一次就會產(chǎn)生兩種不同的細胞亞型,，TacA是在其中一種類型細胞中產(chǎn)生的,。研究者Chien表示，我們使用生化和蛋白質(zhì)純化技術(shù)鑒別出了TacA的哪一部分對于ClpXP的降解至關(guān)重要,。隨后通過構(gòu)建TacA的突變體我們發(fā)現(xiàn),，在細胞中表達TacA時，這些細胞并不能發(fā)育成為兩種正確類型的細胞,。因為發(fā)育的改變對于致病菌入侵宿主至關(guān)重要,，這些研究進展或許為將來開發(fā)新型抗生素提供希望，相關(guān)研究由美國國立綜合醫(yī)學(xué)科學(xué)研究院提供資助,。（生物谷Bioon.com）
doi:10.1111/mmi.12166
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Regulated proteolysis of a transcription factor complex is critical to cell cycle progression in Caulobacter crescentus
Kasia G. Gora1,2,†, Amber Cantin3,†, Matthew Wohlever1, Kamal K. Joshi3,4, Barrett S. Perchuk1, Peter Chien3,4,*, Michael T. Laub1,2,*
Cell cycle transitions are often triggered by the proteolysis of key regulatory proteins. In Caulobacter crescentus, the G1-S transition involves the degradation of an essential DNA-binding response regulator, CtrA, by the ClpXP protease. Here, we show that another critical cell cycle regulator, SciP, is also degraded during the G1-S transition, but by the Lon protease. SciP is a small protein that binds directly to CtrA and prevents it from activating target genes during G1. We demonstrate that SciP must be degraded during the G1-S transition so that cells can properly activate CtrA-dependent genes following DNA replication initiation and the reaccumulation of CtrA. These results indicate that like CtrA, SciP levels are tightly regulated during the Caulobacter cell cycle. In addition, we show that formation of a complex between CtrA and SciP at target promoters protects both proteins from their respective proteases. Degradation of either protein thus helps trigger the destruction of the other, facilitating a cooperative disassembly of the complex. Collectively, our results indicate that ClpXP and Lon each degrade an important cell cycle regulator, helping to trigger the onset of S phase and prepare cells for the subsequent programmes of gene expression critical to polar morphogenesis and cell division.
