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Related Concept Videos

Hemoglobin01:24

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.
When all four heme groups are bound to oxygen, the resulting molecule is called oxyhemoglobin. As a result, arterial blood...
Gene Families01:57

Gene Families

Gene families consist of groups of genes proposed to have originated from a common ancestor. Typically these arise through events in which a gene or genes are mistakenly duplicated during cell division. Unlike their parent genes (which are subject to selection pressure to maintain function), these gene copies do not need to preserve their sequences and may evolve at a relatively faster rate.
Occasionally these regions can be adapted to take on new roles within the organism, becoming novel genes...
Histone Modification02:32

Histone Modification

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 deacetylase,...
Histone Modification02:32

Histone Modification

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 deacetylase,...
Covalently Linked Protein Regulators02:04

Covalently Linked Protein Regulators

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.
Globular and Fibrous Proteins02:21

Globular and Fibrous Proteins

Many proteins can be classified into two distinct subtypes - globular or fibrous. These two types differ in their shapes and solubilities.
Globular proteins are also known as spheroproteins and typically are approximately round in shape. They contain a mix of amino acid types and contain differing sequences in their primary structures. Globular proteins have many different functions, such as enzymes, cellular messengers, and molecular transporters. These roles often require the proteins to be...

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Related Experiment Video

Updated: May 12, 2026

Measurement of Heme Synthesis Levels in Mammalian Cells
09:43

Measurement of Heme Synthesis Levels in Mammalian Cells

Published on: July 9, 2015

Facile heme vinyl posttranslational modification in a hemoglobin.

Matthew R Preimesberger1, Belinda B Wenke, Lukas Gilevicius

  • 1T. C. Jenkins Department of Biophysics, Johns Hopkins University , Baltimore, Maryland 21218, United States.

Biochemistry
|April 24, 2013
PubMed
Summary

Cyanobacterial hemoglobin (GlbN) covalently modifies its heme group, forming a hybrid b/c heme. Researchers engineered variants to understand this robust heme modification, revealing insights into its natural rarity.

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Last Updated: May 12, 2026

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Published on: July 9, 2015

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Published on: May 5, 2022

Area of Science:

  • Biochemistry
  • Protein Engineering
  • Cyanobacterial Biology

Background:

  • Heme is a crucial prosthetic group in many proteins and enzymes.
  • C-type cytochromes feature posttranslational covalent attachment of heme to the polypeptide chain.
  • The cyanobacterial hemoglobin (GlbN) from Synechocystis sp. PCC 6803 exhibits unique b heme covalent modification.

Purpose of the Study:

  • To investigate the determinants of spontaneous b heme covalent modification in Synechocystis GlbN.
  • To explore the engineering potential of histidine-heme cross-linking in GlbN variants.
  • To understand the reasons for the rarity of histidine-heme linkages in natural proteins.

Main Methods:

  • Site-directed mutagenesis to create Synechocystis GlbN variants (L79H/H117A and L79H).
  • Analysis of heme binding affinity and cross-linking formation in engineered GlbN variants.
  • Characterization of the posttranslational modification products, including bis-alkylated adducts.

Main Results:

  • The L79H/H117A GlbN variant formed a cross-link between histidine at position 79 and the heme 4-vinyl substituent.
  • The L79H GlbN variant formed both the native His117-heme linkage and a new His79-heme linkage, creating a bis-alkylated adduct.
  • Engineered GlbN variants demonstrate the robustness and engineerability of histidine-heme modification.

Conclusions:

  • The histidine-heme modification in GlbN is a spontaneous electrophilic addition occurring in the ferrous state.
  • The study successfully engineered novel bis-alkylated GlbN adducts, highlighting the reaction's robustness.
  • The rarity of this modification in nature is likely due to negative selection pressures.