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細菌のDnaCヘリケースローダーは,DnaBのリングブレーカーである

Ernesto Arias-Palomo¹, Valerie L O'Shea, Iris V Hood

¹Department of Molecular and Cell Biology, California Institute for Quantitative Biosciences, University of California, Berkeley, Berkeley, CA 94720, USA.

|April 9, 2013

まとめ

バクテリアのDNA複製はヘリカーゼ負荷に依存しています. 研究者らは,DnaCローダータンパク質がDnaBヘリケースリングを再構成する方法を発見し,DNAの複合組成を解き放つための保存されたメカニズムを明らかにしました.

科学分野:

分子生物学は分子生物学である.
構造生物学構造生物学とは
バイオケミストリーバイオケミストリー

背景:

AAA+ ATPasesはDNA複製に不可欠であり,ヘクサメリクリング状のヘリコースを形成する.
負荷タンパク質によってこれらのヘリカーズのDNAへの負荷は,細胞生物にとって不可欠である.

研究の目的:

DnaCタンパク質によるE. coli DnaBヘリアースの負荷の構造的メカニズムを解明する.
DnaB⋅DnaC複合体が,DNA結合のためのヘリケースリングをどのように再構成するかを理解するために.

主な方法:

電子顕微鏡と小角X線散射 (SAXS) を使用したDnaB⋅DnaC複合体のATP結合構造の決定.
DnaC AAA+の折りたたみとその孤立ドメインがヘリカーゼの負荷と活動における役割を調査する.

主要な成果:

完ぺきなDnaB⋅DnaC複合体 (480 kDa dodecamer) は,スパイラル構成のDnaCで3層のアセンブリを形成する.
DnaCはDnaBを改造し,ヘリケースリングの断裂を生み出し,DnaCの完全なAAA+折りたたみとは独立したプロセスです.
隔離されたDnaC結合ドメインは,DnaBをDNAに効果的にロードし,in vitroでヘリコース活性を増強します.

結論:

DnaCによるバクテリアのヘリケーゼ負荷は,真核ポリメラーゼのクランプロードとメカニズム的に類似しています.
バクテリアの複製ヘリカーゼは,ヘクサメリクモータードメインによるDNAの負荷と解約を制御する自己調節要素を持っています.

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