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Protein-protein Interfaces

Protein-protein Interfaces

Many proteins form complexes to carry out their functions, making protein-protein interactions (PPIs) essential for an organism's survival. Most PPIs are stabilized by numerous weak noncovalent chemical forces. The physical shape of the interfaces determines the way two proteins interact. Many globular proteins have closely-matching shapes on their surfaces, which form a large number of weak bonds. Additionally, many PPIs occur between two helices or between a surface cleft and a polypeptide...

Protein-Protein Interfaces

Protein-Protein Interfaces

Many proteins form complexes to carry out their functions, making protein-protein interactions (PPIs) essential for an organism's survival. Most PPIs are stabilized by numerous weak noncovalent chemical forces. The physical shape of the interfaces determines the way two proteins interact. Many globular proteins have closely-matching shapes on their surfaces, which form a large number of weak bonds. Additionally, many PPIs occur between two helices or between a surface cleft and a polypeptide...

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...

Protein Networks

Protein Networks

An organism can have thousands of different proteins, and these proteins must cooperate to ensure the health of an organism. Proteins bind to other proteins and form complexes to carry out their functions. Many proteins interact with multiple other proteins creating a complex network of protein interactions.
These interactions can be represented through maps depicting protein-protein interaction networks, represented as nodes and edges. Nodes are circles that are representative of a protein,...

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...

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Related Experiment Video

Updated: Jun 25, 2026

Analyzing Protein Architectures and Protein-Ligand Complexes by Integrative Structural Mass Spectrometry

Analyzing Protein Architectures and Protein-Ligand Complexes by Integrative Structural Mass Spectrometry

Published on: October 15, 2018

Interaction between protein subunits from model studies.

¹Department of Physical Chemistry, The Hebrew University, Jerusalem, Israel.

Biophysical Journal

|February 13, 2009

Summary

A molecular model reveals electrostatic forces stabilize hemoglobin tetramers. This explains why myoglobin, unlike hemoglobin, doesn't form such structures, offering insights into protein assembly.

Area of Science:

Biochemistry
Molecular Biology
Structural Biology

Background:

Hemoglobin is a tetrameric protein crucial for oxygen transport.
Myoglobin, a related protein, functions as a monomer.
Understanding the forces governing hemoglobin subunit assembly is key to protein structure-function relationships.

Purpose of the Study:

To investigate the role of electrostatic interactions in hemoglobin subunit association.
To explain the quaternary structure differences between hemoglobin and myoglobin.
To correlate primary structure variations with tetramer stability across species.

Main Methods:

Construction of a molecular model of hemoglobin.
Visualization of amino acid residue relationships within the hemoglobin molecule.

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Analyzing Protein Architectures and Protein-Ligand Complexes by Integrative Structural Mass Spectrometry

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Comparative analysis of hemoglobin primary structures from different species.

Main Results:

The molecular model suggests significant electrostatic forces hold hemoglobin subunits together.
This electrostatic interaction model explains why myoglobin does not form a tetramer.
The model is consistent with the stable tetrameric structure of mammalian hemoglobins and the weak association of lamprey hemoglobin chains.

Conclusions:

Electrostatic forces are critical for the formation and stability of hemoglobin tetramers.
The proposed model provides a structural basis for the distinct quaternary structures of hemoglobin and myoglobin.
Allosteric effects in oxygen binding differ between hemoglobin H and normal hemoglobin due to structural variations.