title: L25 functions as a conserved ribosomal docking site shared by nascent chain-associated complex and signal-recognition particle.
abstract: The nascent chain-associated complex (NAC) is a dimeric protein complex of archaea and eukarya that interacts with ribosomes and translating polypeptide chains. We show that, in yeast, NAC and the signal-recognition particle (SRP) share the universally conserved ribosomal protein L25 as a docking site, which is in close proximity to the ribosomal exit tunnel. The amino-terminal segment of beta-NAC was found to be required for L25 binding. Purified NAC can prevent protein aggregation in vitro and thus shows certain properties of a molecular chaperone. Interestingly, the alpha-subunit of NAC interacts with the 54 kDa subunit of SRP. Consistent with a regulatory role of NAC in protein translocation into the endoplasmic reticulum (ER), we find that deletion of NAC results in an induction of the ER stress-response pathway. These results identify L25 as a conserved interaction platform for specific cytosolic factors that guide nascent polypeptides to their proper cellular destination.
authors.affiliation: Department of Cellular Biochemistry, Max Planck Institute of Biochemistry, Martinsried, Germany.
authors.forename: Silke
authors.initials: S
authors.lastname: Grallath
authors.forename: Juliane P
authors.initials: JP
authors.lastname: Schwarz
authors.forename: Ulrike M K
authors.initials: UM
authors.lastname: Böttcher
authors.forename: Andreas
authors.initials: A
authors.lastname: Bracher
authors.forename: F Ulrich
authors.initials: FU
authors.lastname: Hartl
authors.forename: Katja
authors.initials: K
authors.lastname: Siegers
mesh_terms: D019843:Archaeal Proteins / Q000235:genetics / Q000378:metabolism; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D046912:Multiprotein Complexes; D014176:Protein Biosynthesis; D017434:Protein Structure, Tertiary; D021122:Protein Subunits / Q000235:genetics / Q000378:metabolism; D012269:Ribosomal Proteins / Q000235:genetics / Q000378:metabolism*; D012270:Ribosomes / Q000378:metabolism*; D018271:Signal Recognition Particle / Q000378:metabolism*; D020798:Two-Hybrid System Techniques
chemical_list: D019843:Archaeal Proteins; D005656:Fungal Proteins; D046912:Multiprotein Complexes; D021122:Protein Subunits; D012269:Ribosomal Proteins; D018271:Signal Recognition Particle; C031127:ribosomal protein L25