title: An essential dimer-forming subregion of the endoplasmic reticulum stress sensor Ire1.
abstract: The luminal domain of the type I transmembrane protein Ire1 senses endoplasmic reticulum stress by an undefined mechanism to up-regulate the signalling pathway for the unfolded protein response. Previously, we proposed that the luminal domain of yeast Ire1 is divided into five subregions, termed subregions I-V sequentially from the N-terminus. Ire1 lost activity when internal deletions of subregion II or IV were made. In the present paper, we show that partial proteolysis of a recombinant protein consisting of the Ire1 luminal domain suggests that subregions II-IV are tightly folded. We also show that a recombinant protein of subregions II-IV formed homodimers, and that this homodimer formation was impaired by an internal deletion of subregion IV. Furthermore, recombinant fragments of subregion IV exhibited a self-binding ability. Therefore, although its sequence is little conserved evolutionarily, subregion IV plays an essential role to promote Ire1 dimer formation.
authors.affiliation: Graduate School of Biological Sciences, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, Nara 630-0192, Japan.
authors.forename: Daisuke
authors.initials: D
authors.lastname: Oikawa
authors.forename: Yukio
authors.initials: Y
authors.lastname: Kimata
authors.forename: Masato
authors.initials: M
authors.lastname: Takeuchi
authors.forename: Kenji
authors.initials: K
authors.lastname: Kohno
mesh_terms: D000595:Amino Acid Sequence; D017124:Conserved Sequence; D019281:Dimerization; D004220:Disulfides / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D006031:Glycosylation; D008562:Membrane Glycoproteins / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism; D017434:Protein Structure, Tertiary; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism; D017384:Sequence Deletion
chemical_list: D004220:Disulfides; D008562:Membrane Glycoproteins; D029701:Saccharomyces cerevisiae Proteins; C082863:IRE1 protein, S cerevisiae; D017346:Protein Serine-Threonine Kinases