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Conservation of Protein Domains Over Different Proteins

Conservation of Protein Domains Over Different Proteins

Protein domains are small structurally independent units that are part of a single amino acid chain. Although these domains are often structurally independent, they may rely on synergistic effects to perform their functions as part of a larger protein. Protein domains may be conserved within the same organism, as well as across different organisms.
A limited set of protein domains often duplicate and recombine during evolution. These domains can be organized in different combinations to...

Protein and Protein Structure

Protein and Protein Structure

Proteins are one of the most abundant organic molecules in living systems and have the most diverse range of functions of all macromolecules. Proteins may be structural, regulatory, contractile, or protective. They may serve in transport, storage, or membranes; or they may be toxins or enzymes. Their structures, like their functions, vary greatly. They are all, however, amino acid polymers arranged in a linear sequence.
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Hemoglobin

Hemoglobin

Hemoglobin is a globular protein made up of four subunits. Two of these subunits are alpha chains, and the other two are beta chains. Each subunit contains a molecule of heme, which has an iron atom and can bind to oxygen. When an oxygen molecule binds to one heme group, it changes the shape of hemoglobin, making it easier for the other heme groups to bind oxygen as well.
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Conservation of Protein Domains

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Conserved Binding Sites

Conserved Binding Sites

Many proteins’ biological role depends on their interactions with their ligands, small molecules that bind to specific locations on the protein known as ligand-binding sites. Ligand-binding sites are often conserved among homologous proteins as these sites are critical for protein function.
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Protein Families

Protein Families

Protein families are groups of homologous proteins; that is, they have similarities in amino acid sequences and three-dimensional structures. Protein families usually occur because of gene duplication, where an additional copy of a gene is inserted into the genome of an organism. Mutations that change the amino acids but still allow the protein to be properly synthesized, will lead to new protein family members. If these new proteins contain similar amino acids in key...

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Related Experiment Video

Updated: Feb 4, 2026

Production, Crystallization, and Structure Determination of the IKK-binding Domain of NEMO

Production, Crystallization, and Structure Determination of the IKK-binding Domain of NEMO

Published on: December 28, 2019

The Streptococcus pyogenes Shr protein captures human hemoglobin using two structurally unique binding domains.

Ramsay Macdonald¹, Duilio Cascio², Michael J Collazo²

¹From the Department of Chemistry and Biochemistry,; UCLA-DOE Institute of Genomics and Proteomics and.

The Journal of Biological Chemistry

|October 11, 2018

Summary

Streptococcus pyogenes uses the Shr protein to capture hemoglobin (Hb) via two hemoglobin-interacting domains (HIDs). This study reveals the unique structure and function of these HIDs in bacterial iron acquisition.

Keywords:

DUF1533 Shr Streptococcus pyogenes (S. pyogenes)X-ray crystallography bacterial pathogen hemoglobin isothermal titration calorimetry (ITC)nuclear magnetic resonance (NMR)receptor

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Related Experiment Videos

Last Updated: Feb 4, 2026

Production, Crystallization, and Structure Determination of the IKK-binding Domain of NEMO

Production, Crystallization, and Structure Determination of the IKK-binding Domain of NEMO

Published on: December 28, 2019

Purification of a High Molecular Mass Protein in Streptococcus mutans

Purification of a High Molecular Mass Protein in Streptococcus mutans

Published on: September 14, 2019

Staphylococcus aureus Growth using Human Hemoglobin as an Iron Source

Staphylococcus aureus Growth using Human Hemoglobin as an Iron Source

Published on: February 7, 2013

Area of Science:

Microbiology
Structural Biology
Biochemistry

Background:

Bacterial pathogens require host iron for infection.
Hemoglobin (Hb) is a primary iron source in hosts.
Streptococcus pyogenes utilizes the Shr protein for Hb capture.

Purpose of the Study:

Elucidate the mechanism of Hb capture by the S. pyogenes Shr protein.
Characterize the structure and function of the Hb-binding modules within Shr.

Main Methods:

Nuclear Magnetic Resonance (NMR) spectroscopy
Biochemical assays
X-ray crystallography (1.5 Å resolution)
Site-directed mutagenesis

Main Results:

Shr binds Hb via two autonomously folded domains: HID1 and HID2.
HID2 possesses a unique Hb-binding domain structure.
A conserved tyrosine residue in both HIDs is crucial for Hb binding.
HID2 exhibits higher affinity for Hb than HID1.
Two Shr receptors engage the Hb tetramer.
A third, previously uncharacterized domain links HID2 to the NEAT1 heme-binding domain.

Conclusions:

The two hemoglobin-interacting domains (HIDs) of Shr are key for Hb binding and capture.
Structural and biochemical data reveal the unique nature of Hb-Shr interactions.
A linker domain likely facilitates heme transfer from Hb to NEAT1.