Leghemoglobin and Rhizobium Respiration

Appleby, Cyril A.

doi:10.1146/annurev.pp.35.060184.002303

Cited by 588 publications

(269 citation statements)

References 122 publications

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“…That report is rather unusual because the reverse has commonly been observed, i.e. a reduction in nodule Lb concentration from oxidation reactions often leads to a dec1inein nitrogenase activity due to Lb's inability to support high levels of bacteroid respiration (Appleby, 1984). In fact, it has been demonstrated that with high Lb concentration in nodules, a high level of nitrogenase activity was maintained; however as Lb concentration dec1ined 0305-7364/95/010049+06 $08.00/0 from oxidation by excess 02' nitrogenase activity also dec1ined (Dakora, Appleby and Atkins, 1991).…”

Section: Introductionmentioning

confidence: 85%

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A functional relationship between leghaemoglobin and nitrogenase based on novel measurements of the two proteins in legume root nodules

Dakora

1995

Annals of Botany

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A combination of physiological and structural measurements made on nodulated cowpea and soybean plants cultured with roots in different p02 permitted the expression of da ta in various ways. Values of leghemoglobin concentration and nitrogenase activity from the two legurnes were expressed conventionally either on a per plant or per gram nodule fresh weight basis, and where microscopy was done, on the basis of nitrogenase-containing, N 2-fixing units (i.e. per bacteroid, per infected cell, or per gram infected tissue). In both legumes, acetylene reduction, N fixed and ureide content expressed on the basis of whole plants or per nitrogenase-containing units were very significantly correlated with values ofleghaemoglobin concentrations expressed in a similar manner. The use of mathematical correlations in this study involving leghaemoglobin concentrations and various indices of N 2 fixation indicated a strong functional relationship between the two pro teins in symbiotic legumes. These findings confirm previous suggestions that leghaemoglobin and the nitrogenase complex are two pro teins closely associated with N 2-fixingefficiency in legurne root nodules.

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Section: Introductionmentioning

confidence: 85%

“…Leghaemoglobin (Lb) is a hemoprotein in N 2-fixing nodules which facilitates 02 diffusion to respiring bacteroids in infected cells (Appleby, 1984). The ATP produced from bacteroid respiration via oxidative phosphorylation is used to reduce N 2 to form NH 3 .…”

Section: Introductionmentioning

confidence: 99%

A functional relationship between leghaemoglobin and nitrogenase based on novel measurements of the two proteins in legume root nodules

Dakora

1995

Annals of Botany

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“…Lbs are the most abundant soluble proteins in nodules ( e.g . in soybean nodules their concentration is as high as 3 mM) 16, 42 . The x-ray analysis of lupin Lb revealed that the tertiary structure of Lbs was remarkably similar to that of the sperm whale myoglobin 43 .…”

Section: Introductionmentioning

confidence: 99%

Rice (Oryza) hemoglobins

2014

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Hemoglobins (Hbs) corresponding to non-symbiotic (nsHb) and truncated (tHb) Hbs have been identified in rice ( Oryza). This review discusses the major findings from the current studies on rice Hbs. At the molecular level, a family of the nshb genes, consisting of hb1, hb2, hb3, hb4 and hb5, and a single copy of the thb gene exist in Oryza sativa var. indica and O. sativa var. japonica, Hb transcripts coexist in rice organs and Hb polypeptides exist in rice embryonic and vegetative organs and in the cytoplasm of differentiating cells. At the structural level, the crystal structure of rice Hb1 has been elucidated, and the structures of the other rice Hbs have been modeled. Kinetic analysis indicated that rice Hb1 and 2, and possibly rice Hb3 and 4, exhibit an extremely high affinity for O 2, whereas rice Hb5 and tHb possibly exhibit a low to moderate affinity for O 2. Based on the accumulated information on the properties of rice Hbs and data from the analysis of other plant and non-plant Hbs, it is likely that Hbs play a variety of roles in rice organs, including O 2-transport, O 2-sensing, NO-scavenging and redox-signaling. From an evolutionary perspective, an outline for the evolution of rice Hbs is available. Rice nshb and thb genes vertically evolved through different lineages, rice nsHbs evolved into clade I and clade II lineages and rice nshbs and thbs evolved under the effect of neutral selection. This review also reveals lacunae in our ability to completely understand rice Hbs. Primary lacunae are the absence of experimental information about the precise functions of rice Hbs, the properties of modeled rice Hbs and the cis-elements and trans-acting factors that regulate the expression of rice hb genes, and the partial understanding of the evolution of rice Hbs.

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“…In plants, three types of Hbs have been identified: symbiotic, non-symbiotic (nsHbs) and truncated Hbs (tHbs) [22]. Symbiotic Hbs are synthesized in root nodules of nitrogen fixing plants, and their main function is to facilitate the diffusion of O 2 to respiring bacteroids [1,2]. Plant tHbs are short versions of the classical globin fold.…”

Section: Introductionmentioning

confidence: 99%

Modeling the tertiary structure of a maize (Zea mays ssp. mays) non-symbiotic hemoglobin

Saenz-Rivera

Sarath

Arredondo‐Peter

2004

Plant Physiology and Biochemistry

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Modeling the tertiary structure of a maize (Zea mays ssp. mays) nonsymbiotic hemoglobin" (2004 AbstractThe tertiary structure of a maize (Zea mays ssp. mays) non-symbiotic hemoglobin (Hbm) was modeled using computer tools and the known tertiary structure of rice Hb1 as a template. This method was tested by predicting the tertiary structure of soybean leghemoglobin a (Lba) using rice Hb1 as a template. The tertiary structures of the predicted and native Lba were similar, indicating that our computer methods could reliably predict the tertiary structures of plant Hbs. We next predicted the tertiary structure of Hbm. Hbm appears to have a long pre-helix A and a large CD-loop. The positions of the distal and proximal His are identical in Hbm and rice Hb1, which suggests that heme-Fe is hexacoordinate in Hbm and that the kinetic properties of Hbm and rice Hb1 are expected to be very similar, i.e. that Hbm has a high O 2 -affinity. Thermostability analysis showed that Hbm CD-loop is unstable and may provide mobility to amino acids located at the heme pocket for both ligand binding and stabilization and heme-Fe coordination. Analysis of the C-terminal half of Hbm showed the existence of a pocket-like region (the N/C cavity) where interactions with organic molecules or proteins could be possible. Lys K94 protrudes into the N/C cavity, suggesting that K94 may sense the binding of molecules to the N/C cavity. Thus, it is likely that the instability of the CD-loop and the possibility of binding molecules to the N/C cavity are essential for positioning amino acids in the heme pocket and in regulating Hbm activity and function.

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Leghemoglobin and Rhizobium Respiration

Cited by 588 publications

References 122 publications

A functional relationship between leghaemoglobin and nitrogenase based on novel measurements of the two proteins in legume root nodules

A functional relationship between leghaemoglobin and nitrogenase based on novel measurements of the two proteins in legume root nodules

Rice (Oryza) hemoglobins

Modeling the tertiary structure of a maize (Zea mays ssp. mays) non-symbiotic hemoglobin

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