ジャーナル: J Mol Biol / 年: 2015 タイトル: Architecture of the Complex Formed by Large and Small Terminase Subunits from Bacteriophage P22. 著者: Reginald McNulty / Ravi Kumar Lokareddy / Ankoor Roy / Yang Yang / Gabriel C Lander / Albert J R Heck / John E Johnson / Gino Cingolani / 要旨: Packaging of viral genomes inside empty procapsids is driven by a powerful ATP-hydrolyzing motor, formed in many double-stranded DNA viruses by a complex of a small terminase (S-terminase) subunit ...Packaging of viral genomes inside empty procapsids is driven by a powerful ATP-hydrolyzing motor, formed in many double-stranded DNA viruses by a complex of a small terminase (S-terminase) subunit and a large terminase (L-terminase) subunit, transiently docked at the portal vertex during genome packaging. Despite recent progress in elucidating the structure of individual terminase subunits and their domains, little is known about the architecture of an assembled terminase complex. Here, we describe a bacterial co-expression system that yields milligram quantities of the S-terminase:L-terminase complex of the Salmonella phage P22. In vivo assembled terminase complex was affinity-purified and stabilized by addition of non-hydrolyzable ATP, which binds specifically to the ATPase domain of L-terminase. Mapping studies revealed that the N-terminus of L-terminase ATPase domain (residues 1-58) contains a minimal S-terminase binding domain sufficient for stoichiometric association with residues 140-162 of S-terminase, the L-terminase binding domain. Hydrodynamic analysis by analytical ultracentrifugation sedimentation velocity and native mass spectrometry revealed that the purified terminase complex consists predominantly of one copy of the nonameric S-terminase bound to two equivalents of L-terminase (1S-terminase:2L-terminase). Direct visualization of this molecular assembly in negative-stained micrographs yielded a three-dimensional asymmetric reconstruction that resembles a "nutcracker" with two L-terminase protomers projecting from the C-termini of an S-terminase ring. This is the first direct visualization of a purified viral terminase complex analyzed in the absence of DNA and procapsid.
名称: Bacteriophage P22 terminase holoenzyme / タイプ: sample / ID: 1000 集合状態: One nonamer of S-terminase binds to two L-terminase subunits Number unique components: 2
分子量
実験値: 287 KDa / 理論値: 287 KDa / 手法: Native MS
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分子 #1: small terminase subunit
分子
名称: small terminase subunit / タイプ: protein_or_peptide / ID: 1 / コピー数: 9 / 集合状態: 9 small subunits : 2 large subunits / 組換発現: Yes
pH: 8 詳細: 20 mM Tris-HCl, 150 mM NaCl, 3 mm DTT, 5% glycerol, 1 mM MgCl2
染色
タイプ: NEGATIVE 詳細: Protein was adsorbed to the grid for 1 minute, blotted, and passed through four consecutive 40 microliter drops of 2% uranyl formate.
グリッド
詳細: 400 mesh copper grids charged with Gatan plasma cleaner
凍結
凍結剤: NONE / 装置: OTHER
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電子顕微鏡法
顕微鏡
FEI TECNAI 12
日付
2015年3月25日
撮影
カテゴリ: CCD フィルム・検出器のモデル: TVIPS TEMCAM-F416 (4k x 4k) 実像数: 44 / 平均電子線量: 20 e/Å2 / 詳細: Images were acquired using Leginon.