To Be or Not To Be T4: Evidence of a Complex Evolutionary Pathway of Head Structure and Assembly in Giant Salmonella Virus SPN3US.
To Be or Not To Be T4: Evidence of a Complex Evolutionary Pathway of Head Structure and Assembly in Giant Salmonella Virus SPN3US.
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DOI：
10.3389/fmicb.2017.02251
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发表时间：
2017
影响因子：
5.2
通讯作者：
Thomas JA
中科院分区：
文献类型：
--
作者：
Ali B;Desmond MI;Mallory SA;Benítez AD;Buckley LJ;Weintraub ST;Osier MV;Black LW;Thomas JA
巨型沙门氏菌噬菌体SPN3US具有240 kb的dsDNA基因组和一个由许多蛋白质组成的大型复杂病毒粒子，其中大多数蛋白质的功能尚不明确。我们最近确定SPN3US与相关巨噬菌体共享一组核心基因，并对18个琥珀突变体进行了测序和表征，以促进其作为遗传模型系统的使用。值得注意的是，SPN3US和相关的巨型噬菌体在其头部含有大量的喷射蛋白，包括多亚基病毒粒子RNA聚合酶（vRNAP），该酶在感染期间随DNA进入宿主细胞。在本研究中，我们利用质谱技术对SPN3US病毒粒子进行了表征，以了解其头部组成及其与相关巨噬菌体和T4噬菌体的共同特征。SPN3US仅与脑头成熟所必需的主要酶、脑头蛋白酶和大端酶亚基同源，与脑头壳形成至关重要的T4蛋白、门蛋白和主要衣壳蛋白同源。在大约50个SPN3US头蛋白中，有8个被发现在一个切割基序上被前体蛋白酶gp245水解。Gp245的c端发生自裂，表明这是相关噬菌体蛋白酶的保守激活和/或成熟特征。对基本头部基因突变体的分析表明，vRNAP的5个亚基必须经过组装才能被纳入前体，尽管组装好的vRNAP必须在DNA包装的衣壳中进行随后的主要构象重排，才能通过~30 Å直径的尾管从注入的DNA中喷射出来进行转录。此外，还发现候选射蛋白gp243在头部组装中起关键作用。我们对vRNAP和gp243突变体的分析突出了巨噬菌体头成熟过程中一个意想不到的两分法：虽然所有分析的巨噬菌体都有一个同源蛋白酶来处理主要的衣壳和门脉蛋白，但处理射蛋白并不总是一个稳定的/决定性的特征。我们在SPN3US和相关噬菌体中发现了一种与前体蛋白酶不同的类似物，进一步暗示了巨大噬菌体头结构和组装的复杂进化途径。
Giant Salmonella phage SPN3US has a 240-kb dsDNA genome and a large complex virion composed of many proteins for which the functions of most are undefined. We recently determined that SPN3US shares a core set of genes with related giant phages and sequenced and characterized 18 amber mutants to facilitate its use as a genetic model system. Notably, SPN3US and related giant phages contain a bolus of ejection proteins within their heads, including a multi-subunit virion RNA polymerase (vRNAP), that enter the host cell with the DNA during infection. In this study, we characterized the SPN3US virion using mass spectrometry to gain insight into its head composition and the features that its head shares with those of related giant phages and with T4 phage. SPN3US has only homologs to the T4 proteins critical for prohead shell formation, the portal and major capsid proteins, as well as to the major enzymes essential for head maturation, the prohead protease and large terminase subunit. Eight of ~50 SPN3US head proteins were found to undergo proteolytic processing at a cleavage motif by the prohead protease gp245. Gp245 undergoes auto-cleavage of its C-terminus, suggesting this is a conserved activation and/or maturation feature of related phage proteases. Analyses of essential head gene mutants showed that the five subunits of the vRNAP must be assembled for any subunit to be incorporated into the prohead, although the assembled vRNAP must then undergo subsequent major conformational rearrangements in the DNA packed capsid to allow ejection through the ~30 Å diameter tail tube for transcription from the injected DNA. In addition, ejection protein candidate gp243 was found to play a critical role in head assembly. Our analyses of the vRNAP and gp243 mutants highlighted an unexpected dichotomy in giant phage head maturation: while all analyzed giant phages have a homologous protease that processes major capsid and portal proteins, processing of ejection proteins is not always a stable/defining feature. Our identification in SPN3US, and related phages, of a diverged paralog to the prohead protease further hints toward a complicated evolutionary pathway for giant phage head structure and assembly.
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影响因子：
5.7
作者：
Fokine, Andrei;Rossmann, Michael G.
通讯作者：
Rossmann, Michael G.
影响因子：
--
作者：
Black, Lindsay W.;Thomas, Julie A.
通讯作者：
Thomas, Julie A.
DOI：
10.1073/pnas.0400444101
发表时间：
2004-04-20
影响因子：
11.1
作者：
Fokine, A;Chipman, PR;Rossmann, MG
通讯作者：
Rossmann, MG
影响因子：
16
作者：
Gleghorn, Michael L.;Davydova, Elena K.;Murakami, Katsuhiko S.
通讯作者：
Murakami, Katsuhiko S.
影响因子：
5.4
作者：
Ceyssens, Pieter-Jan;Minakhin, Leonid;Lavigne, Rob
通讯作者：
Lavigne, Rob