title: Regulation of multispanning membrane protein topology via post-translational annealing.
abstract: The canonical mechanism for multispanning membrane protein topogenesis suggests that protein topology is established during cotranslational membrane integration. However, this mechanism is inconsistent with the behavior of EmrE, a dual-topology protein for which the mutation of positively charged loop residues, even close to the C-terminus, leads to dramatic shifts in its topology. We use coarse-grained simulations to investigate the Sec-facilitated membrane integration of EmrE and its mutants on realistic biological timescales. This work reveals a mechanism for regulating membrane-protein topogenesis, in which initially misintegrated configurations of the proteins undergo post-translational annealing to reach fully integrated multispanning topologies. The energetic barriers associated with this post-translational annealing process enforce kinetic pathways that dictate the topology of the fully integrated proteins. The proposed mechanism agrees well with the experimentally observed features of EmrE topogenesis and provides a range of experimentally testable predictions regarding the effect of translocon mutations on membrane protein topogenesis.
authors.affiliation: Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, United States.
authors.forename: Reid C
authors.initials: RC
authors.lastname: Van Lehn
authors.affiliation: Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, United States.
authors.forename: Bin
authors.initials: B
authors.lastname: Zhang
authors.affiliation: Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, United States.
authors.forename: Thomas F
authors.initials: TF
authors.lastname: Miller
mesh_terms: D017920:Antiporters / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D008954:Models, Biological; D008958:Models, Molecular; D050505:Mutant Proteins / Q000235:genetics / Q000378:metabolism; D011487:Protein Conformation; D011499:Protein Processing, Post-Translational
chemical_list: D017920:Antiporters; D029968:Escherichia coli Proteins; D008565:Membrane Proteins; D050505:Mutant Proteins; C075436:EmrE protein, E coli
keywords: biochemistry; biophysics; dual-topology; membrane protein topology; none; simulation; structural biology; topogenesis