Functions of Cytoplasmic Hemoglobins and Myohemerythrin

Wittenberg, Jonathan B.

doi:10.1007/978-3-642-76418-9_3

Cited by 29 publications

(36 citation statements)

References 109 publications

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“…This observation provides strong evidence for a connection between Ngb and oxidative metabolism and is an additional argument in favour of a prominent role of Ngb in O 2 storage or delivery. This holds in particular for the retina, given its rather high levels of Ngb expression, which approach the same level as that of Mb in muscle (Wittenberg, 1992). As pointed out by Fago et al , an argument against a prominent role of Ngb in O 2 supply in the brain has been its low concentration of only 1 μmol l -1 in total brain extracts (Burmester et al, 2000), which is considered to be much too low to sustain O 2 flow to mitochondria.…”

Section: A Role Of Neuroglobin In O 2 Supply?mentioning

confidence: 99%

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What is the function of neuroglobin?

Burmester¹,

Hankeln

2009

Journal of Experimental Biology

224

215

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SUMMARY For a long time, haemoglobin and myoglobin had been assumed to represent the only globin types of vertebrates. In 2000, however, we discovered a third globin type by mining the genome sequence data. Based on a preferential expression in the nervous system, this globin is referred to as neuroglobin. Despite nine years of research, its function is still uncertain and a number of hypotheses have been put forward. Neuroglobin enhances cell viability under hypoxia and under various types of oxidative stress in transgenic systems, but does not appear to be strongly upregulated in response to stress. A close phylogenetic relationship with invertebrate nerve globins and its positive correlation with the oxidative metabolism and mitochondria suggest a role in O2 supply. In vitro studies and cell culture experiments imply that neuroglobin may detoxify reactive oxygen or nitric oxide. Still other studies propose neuroglobin as being part of a signalling chain that transmits the redox state of the cell or that inhibits apoptosis. Although some functions are more probable than others, we conclude that it is still too early to definitively decide what may be the physiological role(s) of neuroglobin in vertebrates. Nevertheless, there is no doubt that neuroglobin has an essential, conserved function and is beneficial to neurons.

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Section: A Role Of Neuroglobin In O 2 Supply?mentioning

confidence: 99%

“…Globins sporadically occur in glial cells or neurons of various invertebrates and there is little doubt that these nerve globins are involved in O 2 supply Wittenberg, 1992). In fact, the lack of nerve globins reduces the viability of invertebrate neurons under hypoxia.…”

Section: A Role Of Neuroglobin In O 2 Supply?mentioning

confidence: 99%

What is the function of neuroglobin?

Burmester¹,

Hankeln

2009

Journal of Experimental Biology

224

215

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“…The trHb of C. eugametos (an unicellular green alga) is induced in response to activation of photosynthesis, being partly localized along the chloroplast thylakoid membranes (25). P. caudatum trHb has been proposed to support oxygen supply to the mitochondria (26).…”

Section: Trhb Functionsmentioning

confidence: 99%

Truncated Hemoglobins and Nitric Oxide Action

et al. 2003

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SummaryTruncated hemoglobins (trHbs) build a separate subfamily within the hemoglobin superfamily; they are scarcely related by sequence similarity to (non-)vertebrate hemoglobins, displaying amino acid sequences in the 115 -130 residue range. The trHb tertiary structure is based on a 2-on-2 a-helical sandwich, which hosts a unique hydrophobic cavity/tunnel system, traversing the protein matrix, from the molecular surface to the heme distal site. Such a protein matrix system may provide a path for diffusion of ligands to the heme. In Mycobacterium tuberculosis trHbN the heme-bound oxygen molecule is part of an extended hydrogen bond network including the heme distal residues TyrB10 and GlnE11. In vitro experiments have shown that M. tuberculosis trHbN supports efficiently nitric oxide dioxygenation, yielding nitrate. Such a reaction would provide a defense barrier against the nitrosative stress raised by host macrophages during lung infection. It is proposed that the whole protein architecture, the heme distal site hydrogen bonded network, and the unique protein matrix tunnel, are optimally designed to support the pseudo-catalytic role of trHbN in converting the reactive NO species into the harmless NO 3 7 .

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“…Whether the concentration of hemoglobin in Frankia is sufficient for simple facilitation of oxygen diffusion is not clear. An overall concentration of 23 M was found for cultures grown in the absence of combined nitrogen, i.e., under nitrogen-fixing conditions, and such a low concentration may not be sufficient for significant facilitation of O 2 diffusion (26). But if much of the hemoglobin is concentrated in specific regions of the cell such as the area near the plasma membrane, then the concentration would be in the range expected for facilitation of oxygen diffusion.…”

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confidence: 95%