0000000000299456
AUTHOR
Rebecca Keller
showing 4 related works from this author
The GlpF residue Trp219 is part of an amino-acid cluster crucial for aquaglyceroporin oligomerization and function
2018
The vestibule loop regions of aquaglyceroporins are involved in accumulation of glycerol inside the channel pore. Even though most loop regions do not show high sequence similarity among aquaglyceroporins, loop E is highly conserved in aquaglyceroporins, but not in members of the homologous aquaporins. Specifically, a tryptophan residue is extremely conserved within this loop. We have investigated the role of this residue (Trp219) that deeply protrudes into the protein and potentially interacts with adjacent loops, using the E. coli aqualgyeroporin GlpF as a model. Replacement of Trp219 affects the activity of GlpF and impairs the stability of the tetrameric protein. Furthermore, we have id…
When two turn into one: evolution of membrane transporters from half modules
2014
Abstract The recently increasing number of atomic structures for active transporters has not only revealed strong conservation in the architecture of sequence-unrelated transporter families, but also identified a unifying element called the ‘inverted repeat topology,’ which is found in nearly all transporter folds to date. Indeed, most membrane transporters consist of two or more domains with similar structure, so-called repeats. It is tempting to speculate that transporters have evolved by duplication of one repeat followed by gene fusion and modification events. An intriguing question is, whether recent genes encoding such a ‘half-transporter’ still exist as independent folding units. Alt…
The Escherichia coli Envelope Stress Sensor CpxA Responds to Changes in Lipid Bilayer Properties
2015
The Cpx stress response system is induced by various environmental and cellular stimuli. It is also activated in Escherichia coli strains lacking the major phospholipid, phosphatidylethanolamine (PE). However, it is not known whether CpxA directly senses changes in the lipid bilayer or the presence of misfolded proteins due to the lack of PE in their membranes. To address this question, we used an in vitro reconstitution system and vesicles with different lipid compositions to track modulations in the activity of CpxA in different lipid bilayers. Moreover, the Cpx response was validated in vivo by monitoring expression of a PcpxP-gfp reporter in lipid-engineered strains of E. coli. Our comb…
Mutational analyses of YqjA, a Tvp38/DedA protein of E. coli
2015
AbstractMembrane proteins of the DedA/Tvp38 protein family are involved in membrane integrity and virulence of pathogenic organisms. However, the structure and exact function of any member of this large protein family are still unclear. In the present study we analyzed the functional and structural properties of a DedA homolog. Purified YqjA variants from Escherichia coli are detectable in different oligomeric states and specific homo-interaction of YqjA monomers in the membrane were confirmed by formation of a disulfide bond in the C-terminal transmembrane helix. Moreover, alanine scanning mutagenesis exhibited different interaction sites crucial for YqjA activity vs. dimer formation.