title: Both the hydrophobicity and a positively charged region flanking the C-terminal region of the transmembrane domain of signal-anchored proteins play critical roles in determining their targeting specificity to the endoplasmic reticulum or endosymbiotic organelles in Arabidopsis cells.
abstract: Proteins localized to various cellular and subcellular membranes play pivotal roles in numerous cellular activities. Accordingly, in eukaryotic cells, the biogenesis of organellar proteins is an essential process requiring their correct localization among various cellular and subcellular membranes. Localization of these proteins is determined by either cotranslational or posttranslational mechanisms, depending on the final destination. However, it is not fully understood how the targeting specificity of membrane proteins is determined in plant cells. Here, we investigate the mechanism by which signal-anchored (SA) proteins are differentially targeted to the endoplasmic reticulum (ER) or endosymbiotic organelles using in vivo targeting, subcellular fractionation, and bioinformatics approaches. For targeting SA proteins to endosymbiotic organelles, the C-terminal positively charged region (CPR) flanking the transmembrane domain (TMD) is necessary but not sufficient. The hydrophobicity of the TMD in CPR-containing proteins also plays a critical role in determining targeting specificity; TMDs with a hydrophobicity value >0.4 on the Wimley and White scale are targeted primarily to the ER, whereas TMDs with lower values are targeted to endosymbiotic organelles. Based on these data, we propose that the CPR and the hydrophobicity of the TMD play a critical role in determining the targeting specificity between the ER and endosymbiotic organelles.
authors.affiliation: Division of Molecular and Life Sciences, Pohang University of Science and Technology, Pohang 790-784, Korea.
authors.forename: Junho
authors.initials: J
authors.lastname: Lee
authors.forename: Hyunkyung
authors.initials: H
authors.lastname: Lee
authors.forename: Jinho
authors.initials: J
authors.lastname: Kim
authors.forename: Sumin
authors.initials: S
authors.lastname: Lee
authors.forename: Dae Heon
authors.initials: DH
authors.lastname: Kim
authors.forename: Sanguk
authors.initials: S
authors.lastname: Kim
authors.forename: Inhwan
authors.initials: I
authors.lastname: Hwang
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000166:cytology* / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000737:chemistry* / Q000378:metabolism; D002736:Chloroplasts / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D049452:Green Fluorescent Proteins / Q000378:metabolism; D057927:Hydrophobic and Hydrophilic Interactions; D008928:Mitochondria / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D011485:Protein Binding; D021382:Protein Sorting Signals; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D011523:Protoplasts / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D013347:Subcellular Fractions / Q000378:metabolism; D013559:Symbiosis
chemical_list: D029681:Arabidopsis Proteins; D021382:Protein Sorting Signals; D011993:Recombinant Fusion Proteins; D049452:Green Fluorescent Proteins