來自布蘭迪斯大學（Brandeis University），霍德華休斯醫(yī)學院的研究人員揭開了酶這一在細胞活動中扮演著重要角色的成分的生活秘密,，他們利用一種成熟的新技術實時捕捉到了一種關鍵酶變換形狀的圖像,，上演了一幕酶動力學舞蹈的精彩劇目。這一研究成果公布在11月18日的Nature雜志上,。
這一研究在布蘭迪斯大學完成，這是一所私立小型大學,，雖然只有幾十年的歷史,，在美國教育界卻頗有地位,，被譽為“全美最年青的主要研究院大學”,。這所每年用在每名學生身上的經費高達29,500多美元的高等學府,，以理科最為出色,，生物化學(全美排第11),、物理(全美排第30),、化學(全美排第38)及生物,，舉國知名，其他學科,，如計算機科學,、英文、歷史,、政治科學和經濟,，也備受贊揚。領導完成這項研究的就是布蘭迪斯大學的霍德華休斯醫(yī)學院研究員Dorothee Kern博士,。
Kern和她的同事通過實時捕捉酶動力學特征,，發(fā)現(xiàn)這些蛋白并不如之前生命科學研究人員認為的那樣,，直到催化事件發(fā)生才實質性的激活，而是在其催化時——底物結合上來之前就完成了一段動力學變化,。這一研究的重要性在于能說明酶在完成各項重要的催化工作之前的細小變化,。
在Kern等人的這兩篇文章中，研究人員實際上獲得了一種酶在底物不存在的情況下,，形狀或者構造的改變的整體圖像,，Kern表示，“這確實是一種形態(tài)轉變”,，早期的研究只能獲得酶固化后的snapshots,，它們真實的細微變化并不清楚。
這一為期三年的研究是一項突破,，幫助研究人員更加深入了解了酶的動力學特征,，Kern等人多年來一直致力于捕捉酶如何移動，以及如何改變形狀,，她在核磁共振（nuclear magnetic resonance,，NMR）技術應用方面取得了許多經驗，這種技術能檢測到一個蛋白中個體原子的運動,。但是在這項研究中,，研究人員需要更多的實驗技術幫助他們不僅獲得關鍵蛋白的運動情況，還有蛋白的結構變化情況,。他們需要了解這種短暫的,，罕見的酶的形狀——這對于理解以及設計藥物至關重要。
原始出處:
Nature 450, 838-844 (6 December 2007) | doi:10.1038/nature06410; Received 14 April 2007; Accepted 26 October 2007; Published online 18 November 2007
Intrinsic motions along an enzymatic reaction trajectory
Katherine A. Henzler-Wildman1, Vu Thai1, Ming Lei1, Maria Ott3, Magnus Wolf-Watz1,6, Tim Fenn2,6, Ed Pozharski2,6, Mark A. Wilson2,6, Gregory A. Petsko2, Martin Karplus4,5, Christian G. Hübner3,6 & Dorothee Kern1
Department of Biochemistry and Howard Hughes Medical Institute,
Department of Biochemistry, Brandeis University, Waltham, Massachusetts 02454, USA
Institute of Physics, Martin Luther-University Halle-Wittenberg, D-06120 Halle, Germany
Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138, USA
Laboratoire de Chimie Biophysique, ISIS, Université Louis Pasteur, F-67000 Strasbourg, France
Present addresses: University of Umeå, Department of Chemistry, SE-90187 Umeå, Sweden (M.W.-W.); Departments of Molecular and Cellular Physiology and Howard Hughes Medical Institute, Stanford University, Stanford, California 94305, USA (T.F.); Department of Pharmaceutical Sciences, University of Maryland, Baltimore, Maryland 21201, USA (E.P.); Department of Biochemistry and the Redox Biology Center, University of Nebraska, Lincoln, Nebraska 68588, USA (M.A.W.); University at Lübeck, Institute of Physics, 23538 Lübeck, Germany (C.G.H.).
Correspondence to: Christian G. Hübner3,6Dorothee Kern1 Correspondence and requests for materials should be addressed to D.K. (Email: [email protected]) or C.G.H. (Email: [email protected]).
The mechanisms by which enzymes achieve extraordinary rate acceleration and specificity have long been of key interest in biochemistry. It is generally recognized that substrate binding coupled to conformational changes of the substrate–enzyme complex aligns the reactive groups in an optimal environment for efficient chemistry. Although chemical mechanisms have been elucidated for many enzymes, the question of how enzymes achieve the catalytically competent state has only recently become approachable by experiment and computation. Here we show crystallographic evidence for conformational substates along the trajectory towards the catalytically competent 'closed' state in the ligand-free form of the enzyme adenylate kinase. Molecular dynamics simulations indicate that these partially closed conformations are sampled in nanoseconds, whereas nuclear magnetic resonance and single-molecule fluorescence resonance energy transfer reveal rare sampling of a fully closed conformation occurring on the microsecond-to-millisecond timescale. Thus, the larger-scale motions in substrate-free adenylate kinase are not random, but preferentially follow the pathways that create the configuration capable of proficient chemistry. Such preferred directionality, encoded in the fold, may contribute to catalysis in many enzymes.
