Myoglobin was found in the nitrogen-fixing cyanobacterium Nostoc commune. This cyanobacterial myoglobin, referred to as cyanoglobin, was shown to be a soluble hemoprotein of 12.5 kilodaltons with an amino acid sequence that is related to that of myoglobins from two lower eukaryotes, the ciliated protozoa Paramecium caudatum and Tetrahymena pyriformis. Cyanoglobin is encoded by the glbN gene, which is positioned between nifU and nifH-two genes essential for nitrogen fixation-in the genome of Nostoc. Cyanoglobin was detected in Nostoc cells only when they were starved for nitrogen and incubated microaerobically.
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Stability and Folding of the Unusually Stable Hemoglobin from is Subtly Optimized and Dependent on the Key Heme Pocket Residues.
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Department of Biochemistry, University of Delhi South Campus, New Delhi, 110021, India.
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The Roy J. Carver Department of Biochemistry, Biophysics, and Molecular Biology, Iowa State University, Ames, IA 50011, United States. Electronic address:
Hemoglobins (phytoglobins) from rice plants (nsHb1) and from the cyanobacterium Synechocystis (PCC 6803) (SynHb) can reduce hydroxylamine with two electrons to form ammonium. The reaction requires intermolecular electron transfer between protein molecules, and rapid electron self-exchange might play a role in distinguishing these hemoglobins from others with slower reaction rates, such as myoglobin. A relatively rapid electron self-exchange rate constant has been measured for SynHb by NMR, but the rate constant for myoglobin is equivocal and a value for nsHb1 has not yet been measured.
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From the Department of Biochemistry, University of Delhi South Campus, New Delhi 110021, India,
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