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Protein Complexes with Interchangeable Parts

Protein Complexes with Interchangeable Parts

Groups of proteins may form a complex where each protein in this complex has a different role in the overall execution of the complex’s function. Often some of the proteins in the complex can be replaced by a closely related variant to give a complex that contains many of the same components yet is functionally distinct.
The SCF ubiquitin ligase is a protein complex of five individual proteins. This complex attaches ubiquitin to other target proteins to mark them for degradation. In order to...

Protein Complexes with Interchangeable Parts

Protein Complexes with Interchangeable Parts

Groups of proteins may form a complex where each protein in this complex has a different role in the overall execution of the complex’s function. Often some of the proteins in the complex can be replaced by a closely related variant to give a complex that contains many of the same components yet is functionally distinct.
The SCF ubiquitin ligase is a protein complex of five individual proteins. This complex attaches ubiquitin to other target proteins to mark them for degradation. In order to...

Cooperative Allosteric Transitions

Cooperative Allosteric Transitions

Cooperative allosteric transitions can occur in multimeric proteins, where each subunit of the protein has its own ligand-binding site. When a ligand binds to any of these subunits, it triggers a conformational change that affects the binding sites in the other subunits; this can change the affinity of the other sites for their respective ligands. The ability of the protein to change the shape of its binding site is attributed to the presence of a mix of flexible and stable segments in the...

Cooperative Allosteric Transitions

Cooperative Allosteric Transitions

Cooperative allosteric transitions can occur in multimeric proteins, where each subunit of the protein has its own ligand-binding site. When a ligand binds to any of these subunits, it triggers a conformational change that affects the binding sites in the other subunits; this can change the affinity of the other sites for their respective ligands. The ability of the protein to change the shape of its binding site is attributed to the presence of a mix of flexible and stable segments in the...

Cooperative Allosteric Transitions

Cooperative Allosteric Transitions

Cooperative allosteric transitions can occur in multimeric proteins, where each subunit of the protein has its own ligand-binding site. When a ligand binds to any of these subunits, it triggers a conformational change that affects the binding sites in the other subunits; this can change the affinity of the other sites for their respective ligands. The ability of the protein to change the shape of its binding site is attributed to the presence of a mix of flexible and stable segments in the...

Polymer Classification: Stereospecificity

Polymer Classification: Stereospecificity

Polymerization generates chiral centers along the entire backbone of a polymer chain. Accordingly, the stereochemistry of the substituent group has a significant effect on polymer properties. Polymers formed from monosubstituted alkene monomers feature chiral carbons at every alternate position in the polymer backbone. Relative to the predominant orientation of substituents at the adjacent chiral carbons, the polymer can exist in three different configurations: isotactic, syndiotactic, and...

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Related Experiment Video

Updated: Jun 13, 2026

X-Ray Crystallography to Study the Oligomeric State Transition of the Thermotoga maritima M42 Aminopeptidase TmPep1050

X-Ray Crystallography to Study the Oligomeric State Transition of the Thermotoga maritima M42 Aminopeptidase TmPep1050

Published on: May 13, 2020

SecA: a tale of two protomers.

Marios Frantzeskos Sardis¹, Anastassios Economou

¹Institute of Molecular Biology and Biotechnology, Foundation of Research and Technology-Hellas, PO Box 1385, Iraklio, Crete, Greece.

Molecular Microbiology

|May 7, 2010

Summary

The bacterial Sec translocase machinery, crucial for protein transport, has an unclear quaternary structure. Further research is needed to understand the functional states of SecA and SecYEG during protein translocation.

Area of Science:

Cellular biology
Molecular mechanisms of protein transport

Background:

The Sec pathway is essential for bacterial protein translocation across membranes.
Key components include the SecYEG channel and the SecA ATPase motor.
The oligomeric states of SecA and SecYEG in functional complexes are debated.

Purpose of the Study:

To investigate the functionally relevant quaternary states of the Sec translocase complex.
To clarify the assembly and oligomerization of SecA and SecYEG during protein translocation.

Main Methods:

Analysis of existing structural data of SecA and SecYEG complexes.
Review of experimental approaches used to determine oligomeric states.
High-resolution cryo-electron microscopy of SecA-SecYEG complexes.

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The Development and Application of Biophysical Assays for Evaluating Ternary Complex Formation Induced by Proteolysis Targeting Chimeras (PROTACS)

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Published on: January 12, 2024

A Protocol for Computer-Based Protein Structure and Function Prediction

A Protocol for Computer-Based Protein Structure and Function Prediction

Published on: November 3, 2011

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Last Updated: Jun 13, 2026

X-Ray Crystallography to Study the Oligomeric State Transition of the Thermotoga maritima M42 Aminopeptidase TmPep1050

X-Ray Crystallography to Study the Oligomeric State Transition of the Thermotoga maritima M42 Aminopeptidase TmPep1050

Published on: May 13, 2020

The Development and Application of Biophysical Assays for Evaluating Ternary Complex Formation Induced by Proteolysis Targeting Chimeras (PROTACS)

The Development and Application of Biophysical Assays for Evaluating Ternary Complex Formation Induced by Proteolysis Targeting Chimeras (PROTACS)

Published on: January 12, 2024

A Protocol for Computer-Based Protein Structure and Function Prediction

A Protocol for Computer-Based Protein Structure and Function Prediction

Published on: November 3, 2011

Main Results:

SecA exists mainly as a dimer in solution, but dimerization interfaces vary.
The quaternary state of the SecYEG channel within the translocase complex is disputed.
A high-resolution structure of a SecA-SecYEG complex provides a potential snapshot of the machinery.

Conclusions:

The exact quaternary states of SecA and SecYEG during active protein translocation remain elusive.
Detergent usage in structural studies may perturb the native state of the translocase.
Integrated approaches combining new and existing methods are necessary to resolve these functional states.