scholarly journals Chaperoning ribosome assembly

2010 ◽  
Vol 189 (1) ◽  
pp. 11-12 ◽  
Author(s):  
Katrin Karbstein
Keyword(s):  
Protein Folding ◽  
Ribosome Assembly ◽  
Cell Biol ◽  
Nascent Chain ◽  
Cellular Compartments

Chaperones help proteins fold in all cellular compartments, and many associate directly with ribosomes, capturing nascent chains to assist their folding and prevent aggregation. In this issue, new data from Koplin et al. (2010. J. Cell Biol. doi: 10.1083/jcb.200910074) and Albanèse et al. (2010. J. Cell Biol. doi: 10.1083/jcb.201001054) suggest that in addition to promoting protein folding, the chaperones ribosome-associated complex (RAC), nascent chain–associated complex (NAC), and Jjj1 also help in the assembly of ribosomes.

Protein folding in the cell: functions of two families of molecular chaperone, hsp 60 and TF55-TCP1

1993 ◽  
Vol 339 (1289) ◽  
pp. 313-326 ◽  
Keyword(s):  
Protein Folding ◽  
Mechanism Of Action ◽  
Molecular Chaperone ◽  
Polypeptide Chain ◽  
Family Members ◽  
Chain Folding ◽  
Cell Functions ◽  
Cellular Compartments

Two families of molecular chaperone, the hsp 60-GroEL family and the TF55-TCP1 family, have been discovered in evolutionarily related cellular compartments. A member of one of these families, hsp 60, has been shown to play a global role in polypeptide chain folding in mitochondria. We review here studies of both hsp 60 and other family members, discussing their essential physiological roles and mechanism of action.

scholarly journals The ribosome and its role in protein folding: looking through a magnifying glass

2017 ◽  
Vol 73 (6) ◽  
pp. 509-521 ◽  
Author(s):  
Abid Javed ◽  
John Christodoulou ◽  
Lisa D. Cabrita ◽  
Elena V. Orlova
Keyword(s):  
Protein Folding ◽  
Structural Biology ◽  
Polypeptide Chain ◽  
Structure And Function ◽  
Cellular Activity ◽  
Cryo Electron Microscopy ◽  
Nascent Chain ◽  
Exit Tunnel ◽  
Dynamics Simulations ◽  
And Function

Protein folding, a process that underpins cellular activity, begins co-translationally on the ribosome. During translation, a newly synthesized polypeptide chain enters the ribosomal exit tunnel and actively interacts with the ribosome elements – the r-proteins and rRNA that line the tunnel – prior to emerging into the cellular milieu. While understanding of the structure and function of the ribosome has advanced significantly, little is known about the process of folding of the emerging nascent chain (NC). Advances in cryo-electron microscopy are enabling visualization of NCs within the exit tunnel, allowing early glimpses of the interplay between the NC and the ribosome. Once it has emerged from the exit tunnel into the cytosol, the NC (still attached to its parent ribosome) can acquire a range of conformations, which can be characterized by NMR spectroscopy. Using experimental restraints within molecular-dynamics simulations, the ensemble of NC structures can be described. In order to delineate the process of co-translational protein folding, a hybrid structural biology approach is foreseeable, potentially offering a complete atomic description of protein folding as it occurs on the ribosome.

Chaperonin-mediated protein folding: fate of substrate polypeptide

2003 ◽  
Vol 36 (2) ◽  
pp. 229-256 ◽  
Author(s):  
Wayne A. Fenton ◽  
Arthur L. Horwich
Keyword(s):  
Protein Folding ◽  
Hydrogen Exchange ◽  
Structural Changes ◽  
Tertiary Structure ◽  
Nmr Studies ◽  
Central Cavity ◽  
Functional Studies ◽  
Atp Binding And Hydrolysis ◽  
Bacterial Cytoplasm ◽  
Cellular Compartments

1. Chaperonin action – an overview 2302. Polypeptide binding – an essential action 2353. Recognition of non-native polypeptide – role of hydrophobicity 2364. Crystallographic analyses of peptide binding 2375. Topology and secondary and tertiary structure of bound substrate polypeptide – fluorescence, hydrogen exchange and NMR studies 2396. Binding by GroEL associated with a putative unfolding action 2427. A potential action of substrate unfolding driven by ATP/GroES binding 2458. Folding in theciscavity 2479. GroEL–GroES-mediated folding of larger substrate proteins by atransmechanism 24910. Prospects for resolving the conformations and fate of polypeptide in the chaperonin reaction 25111. References 252Chaperonins are megadalton ring assemblies that mediate essential ATP-dependent assistance of protein folding to the native state in a variety of cellular compartments, including the mitochondrial matrix, the eukaryotic cytosol, and the bacterial cytoplasm. Structural studies of the bacterial chaperonin, GroEL, both alone and in complex with its co-chaperonin, GroES, have resolved the states of chaperonin that bind and fold non-native polypeptides. Functional studies have resolved the action of ATP binding and hydrolysis in driving the GroEL–GroES machine through its folding-active and binding-active states, respectively. Yet the exact fate of substrate polypeptide during these steps is only poorly understood. For example, while binding involves multivalent interactions between hydrophobic side-chains facing the central cavity of GroEL and exposed hydrophobic surfaces of the non-native protein, the structure of any polypeptide substrate while bound to GroEL remains unknown. It is also unclear whether binding to an open GroEL ring is accompanied by structural changes in the non-native substrate, in particular whether there is an unfolding action. As a polypeptide-bound ring becomes associated with GroES, do the large rigid-body movements of the GroEL apical domains serve as another source of a potential unfolding action? Regarding the encapsulated folding-active state, how does the central cavity itself influence the folding trajectory of a substrate? Finally, how do GroEL and GroES serve, as recently recognized, to assist the folding of substrates too large to be encapsulated inside the machine? Here, such questions are addressed with the findings available to date, and means of further resolving the states of chaperonin-associated polypeptide are discussed.

scholarly journals Nascent Chain Biology: Translation Dynamics and Cotranslational Protein Folding

2019 ◽  
Vol 59 (3) ◽  
pp. 137-140
Author(s):  
Hideki TAGUCHI ◽  
Yuhei CHADANI ◽  
Tatsuya NIWA
Keyword(s):  
Protein Folding ◽  
Nascent Chain

scholarly journals Cyclophilin 20 is involved in mitochondrial protein folding in cooperation with molecular chaperones Hsp70 and Hsp60.

1995 ◽  
Vol 15 (5) ◽  
pp. 2654-2662 ◽  
Author(s):  
J Rassow ◽  
K Mohrs ◽  
S Koidl ◽  
I B Barthelmess ◽  
N Pfanner ◽  
...  
Keyword(s):  
Protein Folding ◽  
Cyclosporin A ◽  
Molecular Chaperones ◽  
Mitochondrial Protein ◽  
The Matrix ◽  
Inhibitory Drug ◽  
Preprotein Translocation ◽  
Cellular Compartments ◽  
Precursor Molecules

We studied the role of mitochondrial cyclophilin 20 (CyP20), a peptidyl-prolyl cis-trans isomerase, in preprotein translocation across the mitochondrial membranes and protein folding inside the organelle. The inhibitory drug cyclosporin A did not impair membrane translocation of preproteins, but it delayed the folding of an imported protein in wild-type mitochondria. Similarly, Neurospora crassa mitochondria lacking CyP20 efficiently imported preproteins into the matrix, but folding of an imported protein was significantly delayed, indicating that CyP20 is involved in protein folding in the matrix. The slow folding in the mutant mitochondria was not inhibited by cyclosporin A. Folding intermediates of precursor molecules reversibly accumulated at the molecular chaperones Hsp70 and Hsp60 in the matrix. We conclude that CyP20 is a component of the mitochondrial protein folding machinery and that it cooperates with Hsp70 and Hsp60. It is speculated that peptidyl-prolyl cis-trans isomerases in other cellular compartments may similarly promote protein folding in cooperation with chaperone proteins.

Protein quality control at the ribosome: focus on RAC, NAC and RQC

2016 ◽  
Vol 60 (2) ◽  
pp. 203-212 ◽  
Author(s):  
Martin Gamerdinger
Keyword(s):  
Quality Control ◽  
Protein Production ◽  
Protein Quality ◽  
Nascent Polypeptide ◽  
Life And Death ◽  
Ribosomal Tunnel ◽  
Protein Biogenesis ◽  
Nascent Chain ◽  
Cellular Compartments ◽  
Polypeptide Chains

The biogenesis of new polypeptides by ribosomes and their subsequent correct folding and localization to the appropriate cellular compartments are essential key processes to maintain protein homoeostasis. These complex mechanisms are governed by a repertoire of protein biogenesis factors that directly bind to the ribosome and chaperone nascent polypeptide chains as soon as they emerge from the ribosomal tunnel exit. This nascent chain ‘welcoming committee’ regulates multiple co-translational processes including protein modifications, folding, targeting and degradation. Acting at the front of the protein production line, these ribosome-associated protein biogenesis factors lead the way in the cellular proteostasis network to ensure proteome integrity. In this article, I focus on three different systems in eukaryotes that are critical for the maintenance of protein homoeostasis by controlling the birth, life and death of nascent polypeptide chains.

The VES KM: a pathway for protein folding in vivo

2020 ◽  
Vol 92 (1) ◽  
pp. 179-191
Author(s):  
Leonor Cruzeiro
Keyword(s):  
Amino Acids ◽  
Protein Folding ◽  
Protein Structures ◽  
Kinetic Mechanism ◽  
Thermal Bath ◽  
Charged Amino Acids ◽  
Nascent Chain ◽  
Dynamics Simulations ◽  
Positively Charged

AbstractWhile according to the thermodynamic hypothesis, protein folding reproducibility is ensured by the assumption that the native state corresponds to the minimum of the free energy in normal cellular conditions, here, the VES kinetic mechanism for folding in vivo is described according to which the nascent chain of all proteins is helical and the first and structure defining step in the folding pathway is the bending of that initial helix around a particular amino acid site. Molecular dynamics simulations are presented which indicate both the viability of this mechanism for folding and its limitations in the presence of a Markovian thermal bath. An analysis of a set of protein structures formed only of helices and loops suggests that bending sites are correlated with regions bounded, on the N-side, by positively charged amino acids like Lysine and Histidine and on the C-side by negatively charged amino acids like Aspartic acid.

scholarly journals Statistical Evidence for a Helical Nascent Chain

Biomolecules ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 357
Author(s):  
Leonor Cruzeiro ◽  
Andrew C. Gill ◽  
J. Chris Eilbeck
Keyword(s):  
Amino Acids ◽  
Protein Folding ◽  
Amino Acid ◽  
Secondary Structures ◽  
Initial Structure ◽  
The Novel ◽  
Nascent Chain ◽  
Equilibrium Process ◽  
Β Sheets ◽  
Α Helix

We investigate the hypothesis that protein folding is a kinetic, non-equilibrium process, in which the structure of the nascent chain is crucial. We compare actual amino acid frequencies in loops, α-helices and β-sheets with the frequencies that would arise in the absence of any amino acid bias for those secondary structures. The novel analysis suggests that while specific amino acids exist to drive the formation of loops and sheets, none stand out as drivers for α-helices. This favours the idea that the α-helix is the initial structure of most proteins before the folding process begins.

scholarly journals Co-Translational Protein Folding and Sorting in Chloroplasts

Plants ◽  
2020 ◽  
Vol 9 (2) ◽  
pp. 214 ◽  
Author(s):  
Fabian Ries ◽  
Claudia Herkt ◽  
Felix Willmund
Keyword(s):  
Protein Folding ◽  
Protein Synthesis ◽  
Carbon Fixation ◽  
Current Knowledge ◽  
Protein Coding ◽  
Light Reaction ◽  
Fast Kinetics ◽  
Final Maturation ◽  
Nascent Chain ◽  
Early Processing

Cells depend on the continuous renewal of their proteome composition during the cell cycle and in order to replace aberrant proteins or to react to changing environmental conditions. In higher eukaryotes, protein synthesis is achieved by up to five million ribosomes per cell. With the fast kinetics of translation, the large number of newly made proteins generates a substantial burden for protein homeostasis and requires a highly orchestrated cascade of factors promoting folding, sorting and final maturation. Several of the involved factors directly bind to translating ribosomes for the early processing of emerging nascent polypeptides and the translocation of ribosome nascent chain complexes to target membranes. In plant cells, protein synthesis also occurs in chloroplasts serving the expression of a relatively small set of 60–100 protein-coding genes. However, most of these proteins, together with nucleus-derived subunits, form central complexes majorly involved in the essential processes of photosynthetic light reaction, carbon fixation, metabolism and gene expression. Biogenesis of these heterogenic complexes adds an additional level of complexity for protein biogenesis. In this review, we summarize the current knowledge about co-translationally binding factors in chloroplasts and discuss their role in protein folding and ribosome translocation to thylakoid membranes.

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