title: What the N-terminal domain of Atg13 looks like and what it does: a HORMA fold required for PtdIns 3-kinase recruitment.
abstract: Atg13 is a subunit of the Atg1 complex that is involved in autophagy. The middle and C-terminal regions of Atg13 are intrinsically disordered and rich in regulatory phosphorylation sites. Thus far, there have been no structural data for any part of Atg13, and no function assigned to its N-terminal domain. We crystallized this domain, and found that it has a HORMA (Hop1, Rev7, Mad2) fold. We showed that the Atg13 HORMA domain is required for autophagy and for recruitment of the phosphatidylinositol (PtdIns) 3-kinase subunit Atg14, but is not required for Atg1 interaction or Atg13 recruitment to the PAS. The HORMA domain of Atg13 is similar to the closed conformation of the spindle checkpoint protein Mad2. A pair of conserved arginines was identified in the structure, and tested functionally in yeast. These residues are important for autophagy, as mutations abrogate autophagy and block Atg14 recruitment. The location of these Arg residues in the structure suggests that the Atg13 HORMA domain could act as a phosphorylation-dependent conformational switch.
authors.affiliation: Laboratory of Molecular Biology; National Institute of Diabetes and Digestive and Kidney Diseases; National Institutes of Health; Bethesda, MD USA.
authors.forename: Christine C
authors.initials: CC
authors.lastname: Jao
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Ragusa
authors.forename: Robin E
authors.initials: RE
authors.lastname: Stanley
authors.forename: James H
authors.initials: JH
authors.lastname: Hurley
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000737:chemistry* / Q000378:metabolism*; D008958:Models, Molecular; D058539:Phosphatidylinositol 3-Kinase / Q000378:metabolism*; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D013329:Structure-Activity Relationship; D015003:Yeasts / Q000378:metabolism
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D058539:Phosphatidylinositol 3-Kinase
keywords: Atg13; Atg14; HORMA; protein crystallography; protein degradation; protein structure; yeast genetics