PspF‐binding domain PspA_1–144 and the PspA·F complex: New insights into the coiled–coil‐dependent regulation of AAA+ proteins

Abstract

SummaryPhage shock protein A (PspA) belongs to the highy conserved PspA/IM30 family and is a key component of the stress inducible Psp system in Escherichia coli. One of its central roles is the regulatory interaction with the transcriptional activator of this system, the σ 54 enhancer-binding protein PspF, a member of the AAA+ protein family. The PspA/F regulatory system has been intensively studied and serves as a paradigm for AAA+ enzyme regulation by trans-acting factors. However, the molecular mechanism of how exactly PspA controls the activity of PspF and hence σ 54 -dependent expression of the psp genes is still unclear. To approach this question, we identified the minimal PspF-interacting domain of PspA, solved its structure, determined its affinity to PspF and the dissociation kinetics, identified residues that are potentially important for PspF regulation and analyzed effects of their mutation on PspF in vivo and in vitro. Our data indicate that several characteristics of AAA+ regulation in the PspA·F complex resemble those of the AAA+ unfoldase ClpB, with both proteins being regulated by a structurally highly conserved coiledcoil domain. The convergent evolution of both regulatory domains points to a general mechanism to control AAA+ activity for divergent physiologic tasks via coiled-coil domains.

VIPP1 Has a Disordered C-Terminal Tail Necessary for Protecting Photosynthetic Membranes against Stress

“…To exert its function, VIPP1 has been shown to form homooligomeric supercomplex as a functional unit (FVP) on the membranes. Reportedly, the N terminus, rather than the C terminus of VIPP1, is necessary for oligomerization in vitro (Otters et al, 2013), which might be potentially further clarified on the base of crystal structure study of PspA 1-144 (Osadnik et al, 2015). This is consistent with our data showing that Vc does not affect FVP formation directly.…”

The Phage Shock Protein Response

“…The key point for this article is that PspA interacts with PspF to inhibit the ATPase activity it needs to induce an open complex formation at its target promoters. In vitro experiments have also raised the intriguing possibility that this inhibition of PspF can be partially relieved without dissolution of the PspA-PspF complex (73). Even so, complete relief of inhibition requires PspA and PspF to separate.…”

Organization into Higher Ordered Ring Structures Counteracts Membrane Binding of IM30, a Protein Associated with Inner Membranes in Chloroplasts and Cyanobacteria

“…Although the structure of a full-length PspA/IM30 protein has not been resolved yet, both proteins are predicted to mainly consist of ␣-helices, which have a high propensity to form coiled-coil structures (5,16,30). In fact, the recently solved crystal structure of a PspA N-terminal protein fragment clearly shows that this region forms a stable coiled-coil (31). Formation of coiled-coil structures involves leucine zipper-like packing of two ␣-helices, where two amphipathic helices interact via their hydrophobic surface.…”