Bap (Sil1) regulates the molecular chaperone BiP by coupling release of nucleotide and substrate

Rosam, Mathias; Krader, Daniela; Nickels, Christina; Hochmair, Janine; Back, Katrin C.; Agam, Ganesh; Barth, Anders; Zeymer, Cathleen; Hendrix, Jelle; Schneider, Markus; Antes, Iris; Reinstein, Jochen; Lamb, Don C. und Buchner, Johannes (2018): Bap (Sil1) regulates the molecular chaperone BiP by coupling release of nucleotide and substrate. In: Nature Structural & Molecular Biology, Bd. 25, Nr. 1: S. 90-100

Abstract

BiP is the endoplasmic member of the Hsp70 family. BiP is regulated by several co-chaperones including the nucleotide-exchange factor (NEF) Bap (Sil1 in yeast). Bap is a two-domain protein. The interaction of the Bap C-terminal domain with the BiP ATPase domain is sufficient for its weak NEF activity. However, stimulation of the BiP ATPase activity requires full-length Bap, suggesting a complex interplay of these two factors. Here, single-molecule FRET experiments with mammalian proteins reveal that Bap affects the conformation of both BiP domains, including the lid subdomain, which is important for substrate binding. The largely unstructured Bap N-terminal domain promotes the substrate release from BiP. Thus, Bap is a conformational regulator affecting both nucleotide and substrate interactions. The preferential interaction with BiP in its ADP state places Bap at a late stage of the chaperone cycle, in which it coordinates release of substrate and ADP, thereby resetting BiP for ATP and substrate binding.

• Dokumententyp: Zeitschriftenartikel
• Fakultätsübergreifende Einrichtungen: Center for Integrated Protein Science Munich (CIPSM)
• Themengebiete: 500 Naturwissenschaften und Mathematik > 540 Chemie
• ISSN: 1545-9993
• Sprache: Englisch