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Related Concept Videos

Molecular Chaperones and Protein Folding03:00

Molecular Chaperones and Protein Folding

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The native conformation of a protein is formed by interactions between the side chains of its constituent amino acids. When the amino acids cannot form these interactions, the protein cannot fold by itself and needs chaperones. Notably, chaperones do not relay any additional information required for the folding of polypeptides; the native conformation of a protein is determined solely by its amino acid sequence. Chaperones catalyze protein folding without being a part of the folded protein.
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Bacterial Protein Maturation01:26

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Bacterial protein maturation is a tightly regulated process that ensures newly synthesized polypeptides achieve correct functional conformations. This maturation involves a series of modifications, folding events, and quality control steps, often assisted by specialized chaperone proteins.N-Terminal ModificationsThe maturation of bacterial polypeptides begins cotranslationally as the polypeptide exits the ribosome. The first amino acid, N-formylmethionine (fMet), is typically modified at the...
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Cotranslational Protein Translocation01:20

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Translocation of proteins across membranes is an ancient process that occurs even in bacteria and archaebacteria. In fact, the components of the translocation machinery are still conserved between prokaryotes and eukaryotes.
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Proteins can form homomeric complexes with another unit of the same protein or heteromeric complexes with different types.  Most protein complexes self-assemble spontaneously via ordered pathways, while some proteins need assembly factors that guide their proper assembly. Despite the crowded intracellular environment, proteins usually interact with their correct partners and form functional complexes.
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A sizable fraction of proteins destined for ER are first synthesized in the cell cytosol and then transported across the ER membrane–a process called post-translational translocation. Similar to cotranslationally translocated proteins, these proteins also use the Sec translocon complex to enter the ER lumen.
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Detection of the pH-dependent Activity of Escherichia coli Chaperone HdeB In Vitro and In Vivo
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Chaperonin Mechanisms: Multiple and (Mis)Understood?

Amnon Horovitz1, Tali Haviv Reingewertz1, Jorge Cuéllar2

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Annual Review of Biophysics
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Summary
This summary is machine-generated.

Chaperonins like E. coli GroEL are essential protein-folding machines. This review explores their mechanisms, focusing on ongoing debates about substrate specificity and cofactor roles.

Keywords:
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Area of Science:

  • Biochemistry
  • Molecular Biology
  • Cell Biology

Background:

  • Chaperonins are ATP-dependent molecular machines essential for protein folding.
  • They feature a double-ring structure with internal cavities for protein encapsulation.
  • Key examples include GroEL from Escherichia coli and TRiC/CCT from eukaryotes.

Purpose of the Study:

  • To review the current understanding of chaperonin reaction mechanisms.
  • To highlight unresolved questions regarding substrate specificity and cofactor function.
  • To compare the mechanisms of bacterial (GroEL) and eukaryotic (TRiC/CCT) chaperonins.

Main Methods:

  • Comparative analysis of existing literature on chaperonin function.
  • Discussion of experimental evidence and theoretical models.
  • Focus on mechanistic aspects of protein folding assistance.

Main Results:

  • Chaperonins employ ATP hydrolysis to facilitate protein folding within a sequestered environment.
  • Despite architectural similarities, GroEL and TRiC/CCT exhibit distinct reaction mechanisms.
  • Key aspects of their mechanisms, including substrate recognition and cofactor roles, remain debated.

Conclusions:

  • Further research is needed to elucidate the precise mechanisms of chaperonin-mediated protein folding.
  • Understanding these mechanisms is crucial for comprehending cellular protein homeostasis.
  • Debates persist on whether chaperonin action is passive or active and how clients are recognized.