TolC , a macromolecular periplasmic
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چکیده
Calcium everywhere The structure of S100B complexed with the p53 peptide provides the first glimpse of how an EF-hand protein recognizes a transcription factor in order to regulate transcriptional activity. Other examples of EF-hand proteins involving transcription regulation include the down-stream regulatory element antagonist modulator DREAM, which functions as a Ca2+dependent DNA-binding transcriptional repressor24. Clearly Ca2+ signaling has diverse cellular functions ranging from transmembrane and cytoplasmic signal transduction to gene regulation. Ca2+–S100B-mediated regulation of p53 transcription activity provides a possible
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Structures of sequential open states in a symmetrical opening transition of the TolC exit duct.
In bacterial drug resistance and virulence pumps, an inner membrane (IM) transporter and periplasmic adaptor recruit an outer membrane (OM) trimeric TolC exit duct that projects an α-helical tunnel across the periplasm. The TolC periplasmic entrance is closed by densely packed α-helical coiled coils, inner H7/H8, and outer H3/H4, constrained by a hydrogen bond network. On recruitment, these coi...
متن کاملA periplasmic coiled-coil interface underlying TolC recruitment and the assembly of bacterial drug efflux pumps.
Bacteria such as Escherichia coli and Pseudomonas aeruginosa expel antibiotics and other inhibitors via tripartite multidrug efflux pumps spanning the inner and outer membranes and the intervening periplasmic space. A key event in pump assembly is the recruitment of an outer membrane-anchored TolC exit duct by the adaptor protein of a cognate inner membrane translocase, establishing a contiguou...
متن کاملChunnel vision
The Escherichia coli TolC protein is central to toxin export and drug efflux across the inner and outer cell membranes and the intervening periplasmic space. The crystal structure has revealed that TolC assembles into a remarkable α-helical trans-periplasmic cylinder (tunnel) embedded in the outer membrane by a contiguous β-barrel (channel), so providing a large duct open to the outside environ...
متن کاملAntibiotic-sensitive TolC mutants and their suppressors.
The TolC protein of Escherichia coli, through its interaction with AcrA and AcrB, is thought to form a continuous protein channel that expels inhibitors from the cell. Consequently, tolC null mutations display a hypersensitive phenotype. Here we report the isolation and characterization of tolC missense mutations that direct the synthesis of mutant TolC proteins partially disabled in their effl...
متن کاملTransition to the open state of the TolC periplasmic tunnel entrance.
The TolC channel-tunnel spans the bacterial outer membrane and periplasm, providing a large exit duct for protein export and multidrug efflux when recruited by substrate-engaged inner membrane complexes. The sole constriction in the single pore of the homotrimeric TolC is the periplasmic tunnel entrance, which in its resting configuration is closed by dense packing of the 12 tunnel-forming alph...
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