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Published on: February 24, 2011
Myoglobin in a cyanobacterium
M Potts1, S V Angeloni, R E Ebel
1Department of Biochemistry, Virginia Polytechnic Institute and State University, Blacksburg Va 24061.
Science (New York, N.Y.)
|June 19, 1992
Summary
A novel myoglobin, cyanoglobin, was discovered in Nostoc commune, a nitrogen-fixing cyanobacterium. This hemoprotein is linked to eukaryotic myoglobins and appears under nitrogen-starved, microaerobic conditions.
Area of Science:
- Biochemistry
- Microbiology
- Molecular Biology
Background:
- Myoglobins are typically found in muscle tissue of animals, functioning in oxygen transport and storage.
- The presence and function of myoglobin-like proteins in prokaryotes, particularly cyanobacteria, remain less understood.
- Nitrogen fixation in cyanobacteria is a complex process sensitive to oxygen levels.
Purpose of the Study:
- To identify and characterize a myoglobin-like protein in the nitrogen-fixing cyanobacterium Nostoc commune.
- To investigate the genetic basis and expression patterns of this novel cyanobacterial hemoprotein.
- To explore the potential role of cyanoglobin in oxygen homeostasis during nitrogen fixation.
Main Methods:
- Isolation and purification of the hemoprotein from Nostoc commune.
- Biochemical characterization including molecular weight determination (12.5 kDa).
- Amino acid sequencing and comparison with known myoglobins.
- Gene identification (glbN) and genomic localization relative to nitrogen fixation genes (nifU, nifH).
- Detection of cyanoglobin expression under specific environmental conditions (nitrogen starvation, microaerobic incubation).
Main Results:
- A soluble hemoprotein, termed cyanoglobin, was identified in Nostoc commune.
- Cyanoglobin exhibits sequence homology to myoglobins from lower eukaryotes like Paramecium and Tetrahymena.
- The cyanoglobin gene (glbN) is located adjacent to essential nitrogen fixation genes.
- Cyanoglobin is specifically detected in cells under nitrogen-starved and microaerobic conditions.
Conclusions:
- Nostoc commune possesses a unique cyanoglobin with evolutionary links to eukaryotic myoglobins.
- The glbN gene's proximity to nif genes suggests a coordinated role in nitrogen fixation.
- Cyanoglobin expression is regulated by nitrogen availability and oxygen levels, potentially aiding in protecting nitrogenase activity.
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