Structural features of chloroplast trigger factor determined at 2.6 Å resolution. Issue 10 (27th September 2022)

• Record Type: Journal Article
• Authors: Carius, Yvonne; Ries, Fabian; Gries, Karin; Trentmann, Oliver; Lancaster, C. Roy D.; Willmund, Felix
• Is Part Of: Acta crystallographica. Volume 78:Issue 10(2022)
• Page Start: 1259
• Page End: 1272
• Publication Date: 2022-09-27
• Subjects: molecular chaperones -- chaperone trigger factor -- chloroplasts -- Chlamydomonas reinhardtii -- co‐translational folding -- PPIases; X-ray crystallography -- Periodicals; Crystallography -- Periodicals; Molecular biology -- Periodicals; Molecular structure -- Periodicals; Biomolecules -- Structure -- Periodicals; Cytology -- Periodicals; Biomolecules -- Structure; Crystallography; Cytology; Molecular biology; Molecular structure; X-ray crystallography; Periodicals; 548
• DOI: 10.1107/S2059798322009068
• Languages: English
• ISSNs: 2059-7983

Abstract

Abstract : This study describes the structure of the chloroplast ribosome‐associated molecular chaperone trigger factor at 2.6 Å resolution. It is shown that this eukaryotic trigger factor has evolved specific structural features in plants that are distinct from those of the bacterial homolog, contributing to a better understanding of co‐translational protein folding in plastids. Abstract : The folding of newly synthesized polypeptides requires the coordinated action of molecular chaperones. Prokaryotic cells and the chloroplasts of plant cells possess the ribosome‐associated chaperone trigger factor, which binds nascent polypeptides at their exit stage from the ribosomal tunnel. The structure of bacterial trigger factor has been well characterized and it has a dragon‐shaped conformation, with flexible domains responsible for ribosome binding, peptidyl‐prolyl cis – trans isomerization (PPIase) activity and substrate protein binding. Chloroplast trigger‐factor sequences have diversified from those of their bacterial orthologs and their molecular mechanism in plant organelles has been little investigated to date. Here, the crystal structure of the plastidic trigger factor from the green alga Chlamydomonas reinhardtii is presented at 2.6 Å resolution. Due to the high intramolecular flexibility of the protein, diffraction to this resolution was only achieved using a protein that lacked the N‐terminal ribosome‐binding domain. The eukaryotic trigger factor from C. reinhardtii exhibits a comparable dragon‐shaped conformation to its bacterial counterpart. However, the C‐terminal chaperone domain displays distinct charge distributions, with altered positioning of the helical arms and a specifically altered charge distribution along the surface responsible for substrate binding. While the PPIase domain shows a highly conserved structure compared with other PPIases, its rather weak activity and an unusual orientation towards the C‐terminal domain points to specific adaptations of eukaryotic trigger factor for function in chloroplasts.