title: The Sec2 translocase of the chloroplast inner envelope contains a unique and dedicated SECE2 component.
abstract: Biogenesis of chloroplasts involves a series of protein trafficking events. Nuclear-encoded proteins are imported into the organelle, and then trafficked to various chloroplast locations by systems that are directly homologous to bacterial systems. Although the thylakoid-based systems have been studied extensively, much less is known about the systems that reside and function in the inner envelope membrane. One such system, the Sec2 system, is homologous to both the thylakoid-based Sec1 system and bacterial Sec systems, and may mediate both integration and translocation across the inner envelope. At a minimum, this system is expected to include three components, but only two, SCY2 and SECA2, have been identified in Arabidopsis. Bioinformatics and protein modeling were used to identify the protein encoded by At4g38490 as a candidate for the missing component (SECE2). Cellular localization, biochemistry, protein interaction assays in yeast, and co-immunoprecipitation experiments were used to establish that this protein is an integral membrane protein of the inner envelope, and specifically interacts with the SCY2 component in vivo. Sequence analyses indicated that SECE2 proteins are found in a variety of plants, and differ from the thylakoid SECE1 proteins in a stroma-exposed helical domain, which may contribute to their specificity. Finally, a genetic analysis indicated that SECE2 plays an essential role in plant growth and development.
authors.affiliation: Horticultural Sciences Department and Plant Molecular and Cellular Biology, University of Florida, Gainesville, FL, 32611, USA.
authors.forename: Yubing
authors.initials: Y
authors.lastname: Li
authors.affiliation: Department of Botany, University of Wisconsin at Madison, 430 Lincoln Drive, Madison, WI, 53706, USA.
authors.forename: Rajneesh
authors.initials: R
authors.lastname: Singhal
authors.affiliation: Department of Botany, University of Wisconsin at Madison, 430 Lincoln Drive, Madison, WI, 53706, USA.
authors.forename: Isaiah W
authors.initials: IW
authors.lastname: Taylor
authors.affiliation: Department of Botany, University of Wisconsin at Madison, 430 Lincoln Drive, Madison, WI, 53706, USA.
authors.forename: Patrick H
authors.initials: PH
authors.lastname: McMinn
authors.affiliation: Department of Botany, University of Wisconsin at Madison, 430 Lincoln Drive, Madison, WI, 53706, USA.
authors.forename: Xien Yu
authors.initials: XY
authors.lastname: Chua
authors.affiliation: Horticultural Sciences Department and Plant Molecular and Cellular Biology, University of Florida, Gainesville, FL, 32611, USA.
authors.forename: Kenneth
authors.initials: K
authors.lastname: Cline
authors.affiliation: Department of Botany, University of Wisconsin at Madison, 430 Lincoln Drive, Madison, WI, 53706, USA.
authors.forename: Donna E
authors.initials: DE
authors.lastname: Fernandez
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D060365:Chloroplast Proteins / Q000235:genetics / Q000378:metabolism*; D002736:Chloroplasts / Q000235:genetics / Q000378:metabolism*; D015151:Immunoblotting; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D018613:Microscopy, Confocal; D008969:Molecular Sequence Data; D030821:Plants, Genetically Modified; D011485:Protein Binding; D021381:Protein Transport; D000069816:SEC Translocation Channels; D017386:Sequence Homology, Amino Acid; D020524:Thylakoids / Q000235:genetics / Q000378:metabolism*; D020798:Two-Hybrid System Techniques
chemical_list: D029681:Arabidopsis Proteins; D060365:Chloroplast Proteins; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; C557636:SCY2 protein, Arabidopsis; D000069816:SEC Translocation Channels; C000612150:SECE2 protein, Arabidopsis
keywords: Arabidopsis thaliana; Sec translocase; SecYE; chloroplast envelope; protein targeting; subfunctionalization