Abstract
The Phage shock protein (Psp) response is an extracytoplasmic stress response. The central component of this system is PspA, a protein that mediates the physiological response to membrane stress. PspA is also involved in regulating its own transcription and that of the psp operon, forming a positive feedback loop. PspA has been previously shown to oligomerise into higher-order species, including a 36-meric species with ring-like structure. In this study, we demonstrate that the ring-like PspA structures further self-assemble into rod-shaped complexes. These rod-like structures may play a scaffolding role in the maintenance of membrane integrity during phage shock protein response.
Highlights
The Phage shock protein (Psp) response maintains bacterial membrane integrity during extracytoplasmic stress
For the protein sample purified in the presence of CHAPS, the Phage shock protein A (PspA) protein eluted at 43.4 ml and between 67.3 - 108.7 ml, while PspA purified in the absence of CHAPS eluted at 44.3 ml and 59.7 - 109.4 ml
We have demonstrated by electron microscopy that E. coli PspA units self-assemble to form rod-like complexes analogous to those previously observed for C. reinhardtii Vipp1 [24]
Summary
The Phage shock protein (Psp) response maintains bacterial membrane integrity during extracytoplasmic stress. The central component of this system is a 25 kDa protein, which was observed during filamentous phage infection in Escherichia coli but was absent in non-infected cells [1]. This protein was named the Phage shock protein A (PspA) and has been shown to be key to the Psp response [2]. The first is regulated by an upstream σ54-promoter and contains five open-reading frames encoding: PspA, PspB, PspC, PspD and PspE proteins (referred to hereafter as the psp operon) [10]. The third gene is not linked to the psp operon and pspF, but is up-regulated in tandem with the psp operon genes by σ54, PspF, the integration host factor and PspA; this gene was subsequently named pspG [12] [13]
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