title: Protein-protein interactions indicate composition of a 480 kDa SELMA complex in the second outermost membrane of diatom complex plastids.
abstract: Most secondary plastids of red algal origin are surrounded by four membranes and nucleus-encoded plastid proteins have to traverse these barriers. Translocation across the second outermost plastid membrane, the periplastidal membrane (PPM), is facilitated by a ERAD-(ER-associated degradation) derived machinery termed SELMA (symbiont-specific ERAD-like machinery). In the last years, important subunits of this translocator have been identified, which clearly imply compositional similarities between SELMA and ERAD. Here we investigated, via protein-protein interaction studies, if the composition of SELMA is comparable to the known ERAD complex. As a result, our data suggest that the membrane proteins of SELMA, the derlin proteins, are linked to the soluble sCdc48 complex via the UBX protein sUBX. This is similar to the ERAD machinery whereas the additional SELMA components, sPUB und a second Cdc48 copy might indicate the influence of functional constraints in developing a translocation machinery from ERAD-related factors. In addition, we show for the first time that a rhomboid protease is a central interaction partner of the membrane proteins of the SELMA system in complex plastids.
authors.affiliation: Laboratory for Cell Biology, Philipps-Universität Marburg, Marburg, Germany.
authors.forename: Julia B
authors.initials: JB
authors.lastname: Lau
authors.affiliation: Laboratory for Cell Biology, Philipps-Universität Marburg, Marburg, Germany.
authors.forename: Simone
authors.initials: S
authors.lastname: Stork
authors.affiliation: LOEWE Centre for Synthetic Microbiology (SYNMIKRO), Philipps-Universität Marburg, Germany.
authors.forename: Daniel
authors.initials: D
authors.lastname: Moog
authors.affiliation: Laboratory for Cell Biology, Philipps-Universität Marburg, Marburg, Germany.
authors.forename: Julian
authors.initials: J
authors.lastname: Schulz
authors.affiliation: Laboratory for Cell Biology, Philipps-Universität Marburg, Marburg, Germany.|LOEWE Centre for Synthetic Microbiology (SYNMIKRO), Philipps-Universität Marburg, Germany.
authors.forename: Uwe G
authors.initials: UG
authors.lastname: Maier
mesh_terms: D000595:Amino Acid Sequence; D017377:Diatoms / Q000235:genetics* / Q000378:metabolism*; D060746:Endoplasmic Reticulum-Associated Degradation; D007425:Intracellular Membranes / Q000378:metabolism*; D046912:Multiprotein Complexes / Q000378:metabolism*; D018087:Plastids / Q000378:metabolism*; D011485:Protein Binding; D025941:Protein Interaction Mapping; D021381:Protein Transport
chemical_list: D046912:Multiprotein Complexes