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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.
The...
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Covalently Linked Protein Regulators02:04

Covalently Linked Protein Regulators

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Proteins can undergo many types of post-translational modifications, often in response to changes in their environment. These modifications play an important role in the function and stability of these proteins. Covalently linked molecules include functional groups, such as methyl, acetyl, and phosphate groups, and also small proteins, such as ubiquitin. There are around 200 different types of covalent regulators that have been identified.
These groups modify specific amino acids in a protein....
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Phosphorylation01:02

Phosphorylation

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The addition or removal of phosphate groups from proteins is the most common chemical modification that regulates cellular processes. These modifications can affect the structure, activity, stability, and localization of proteins within cells as well as their interactions with other proteins.
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Energy to Drive Translocation01:37

Energy to Drive Translocation

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Mitochondrial protein import is powered by two distinct energy sources: ATP hydrolysis and electrochemical potential across the inner membrane. Newly synthesized precursors are bound by cytosolic chaperones of the Hsp70 family, which guide them to the import receptors on the mitochondrial surface. Utilizing the energy of ATP hydrolysis, Hsp70 chaperones transfer these precursors to the TOM receptors on the mitochondrial outer membrane.
Generally, polypeptides are unfolded by two distinct...
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Histone Modification02:32

Histone Modification

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The histone proteins have a flexible N-terminal tail extending out from the nucleosome. These histone tails are often subjected to post-translational modifications such as acetylation, methylation, phosphorylation, and ubiquitination. Particular combinations of these modifications form “histone codes” that influence the chromatin folding and tissue-specific gene expression.
Acetylation
The enzyme histone acetyltransferase adds acetyl group to the histones. Another enzyme, histone...
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Protein Kinases and Phosphatases02:54

Protein Kinases and Phosphatases

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Proteins undergo chemical modifications that trigger changes in the charge, structure, and conformation of the proteins. Phosphorylation, acetylation, glycosylation, nitrosylation, ubiquitination, lipidation, methylation, and proteolysis are various protein modifications that regulate protein activity. Such modifications are usually enzyme-driven.
Protein kinases
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Studies of Chaperone-Cochaperone Interactions using Homogenous Bead-Based Assay
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Site-specifically Phosphorylated Hsp90C-terminal Domain Variants Provide Access to Deciphering the Chaperone Code.

Oliver Gajsek1,2, Christian F W Becker1, Anne C Conibear3

  • 1Institute of Biological Chemistry, Faculty of Chemistry, University of Vienna, Währingerstraße 39, 1090, Vienna, Austria.

Chemistry (Weinheim an Der Bergstrasse, Germany)
|November 15, 2024
PubMed
Summary

Site-specific phosphorylations in Heat shock protein 90 (Hsp90) C-terminal domain were introduced. These modifications slightly decreased thermal stability but did not significantly alter Hsp90

Keywords:
ChaperonesExpressed Protein Selenoester LigationHsp90Posttranslational modificationsProtein synthesis

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Area of Science:

  • Molecular biology
  • Protein biochemistry
  • Cellular stress response

Background:

  • Heat shock protein 90 (Hsp90) is a crucial molecular chaperone involved in protein folding.
  • Posttranslational modifications (PTMs) on Hsp90, known as the 'chaperone code,' and their effects on Hsp90 function are not fully understood.
  • The Hsp90 C-terminal domain (CTD) is vital for forming the active Hsp90 dimer and interacts with co-chaperones and client proteins.

Purpose of the Study:

  • To investigate the impact of site-specific phosphorylations in the Hsp90 CTD on its structure, stability, and chaperone activity.
  • To develop an efficient method for generating site-specifically modified Hsp90 variants to study the 'chaperone code.'

Main Methods:

  • Expressed protein selenoester ligation (EPSL) was optimized and utilized to introduce site-selective phosphorylations into the Hsp90 CTD.
  • Characterization of modified Hsp90 CTD variants, including assessment of secondary structure, thermal stability, and anti-aggregation activity using model client proteins.

Main Results:

  • Site-specific phosphorylations were successfully introduced into the Hsp90 CTD without altering the native amino acid sequence or overall secondary structure.
  • Combined phosphorylations led to a slight decrease in the thermal stability of the Hsp90 CTD.
  • The introduced phosphorylations did not significantly affect the chaperone activity of the Hsp90 CTD in preventing the aggregation of model client proteins.

Conclusions:

  • Optimized EPSL provides an efficient method for generating site-specifically PTM-modified Hsp90 CTD variants.
  • While C-terminal phosphorylations impact Hsp90 CTD stability, their direct effect on chaperone activity against model clients is minimal.
  • Further research is needed to fully elucidate the role of the 'chaperone code' in Hsp90 function.