Structural and energetic basis of infection by the filamentous bacteriophage IKe
Structural and energetic basis of infection by the filamentous bacteriophage IKe
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DOI：
10.1111/j.1365-2958.2012.08079.x
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发表时间：
2012-06-01
影响因子：
3.6
通讯作者：
Schmid, Franz X.
中科院分区：
文献类型：
--
作者：
Jakob, Roman P.;Geitner, Anne-Juliane;Schmid, Franz X.
丝状噬菌体利用其基因3蛋白的两个N-末端结构域启动大肠杆菌的感染。一个结构域与菌毛相互作用，然后另一个结构域在细胞表面与托拉结合。在噬菌体fd中，这两个结构域彼此紧密结合，这使得噬菌体稳健但无感染性，因为托拉结合位点不可接近。感染的激活需要部分解折叠、结构域分解和脯氨酰异构化。噬菌体IKe感染E. coli的效率低于噬菌体FD。与噬菌体fd不同，噬菌体IKe的菌毛结合结构域和TolA结合结构域在稳定性和折叠方面彼此独立。因此，托拉结合位点总是可接近的，但亲和力非常低。这两个域的结构，通过X-射线晶体学和NMR光谱分析，揭示了一个独特的折叠的N-菌毛结合域和保守的折叠的TolA结合域。缺乏如噬菌体fd中的活化机制和对托拉的低亲和力可能解释了噬菌体IKe的低感染性。他们还解释了为什么在先前的噬菌体fd和噬菌体IKe混合物的共同进化实验中，所有杂交噬菌体都采用了噬菌体fd的上级感染机制。
Filamentous phage use the two N-terminal domains of their gene-3-proteins to initiate infection of Escherichia coli. One domain interacts with a pilus, and then the other domain binds to TolA at the cell surface. In phage fd, these two domains are tightly associated with each other, which renders the phage robust but non-infectious, because the TolA binding site is inaccessible. Activation for infection requires partial unfolding, domain disassembly and prolyl isomerization. Phage IKe infects E. coli less efficiently than phage fd. Unlike in phage fd, the pilus- and TolA-binding domains of phage IKe are independent of each other in stability and folding. The site for TolA binding is thus always accessible, but the affinity is very low. The structures of the two domains, analysed by X-ray crystallography and by NMR spectroscopy, revealed a unique fold for the N-pilus-binding domain and a conserved fold for the TolA-binding domain. The absence of an activation mechanism as in phage fd and the low affinity for TolA probably explain the low infectivity of phage IKe. They also explain why, in a previous co-evolution experiment with a mixture of phage fd and phage IKe, all hybrid phage adopted the superior infection mechanism of phage fd.