PR00188

Plant globin

PRINTS entry
Member databasePRINTS
PRINTS typefamily
Short namePLANTGLOBIN

Description

Leghaemoglobins are haem-proteins, first identified in root nodules of leguminous plants: their physiological role involves fixation of atmospheric nitrogen, formed symbiotically in the nodules by the bacteria Rhizobium
[2]
. The structure of leghaemoglobins is similar to that of haemoglobins and myoglobins, although there is little sequence conservation
[2]
. The protein is largely alpha-helical, eight helices providing the scaffold for a well-defined haem-binding pocket
[2]
. By contrast with the tetrameric mammalian globin assembly, the plant form is monomeric
[1]
.

The structural similarity of leghaemoglobins and haemoglobins has suggested a common evolutionary origin. It was thought that haemoglobins may be found in plants other than legumes
[1]
, and indeed globins have now been identified in the roots of non-leguminous plants, where they have a role in respiratory metabolism in the root cells
[1]
.

PLANTGLOBIN is a 4-element fingerprint that provides a signature for the plant globins. The fingerprint was derived from an initial alignment of 7 sequences: motif 1 includes helix A; motif 2 contains part of helix B and helix C; motif 3 includes helix E and corresponds to the region encoded by PROSITE pattern PLANT_GLOBIN (PS00208), the conserved His of which is one of the iron ligands; and motif 4 contains part of helix G and helix H (structural studies show that various residues from motifs 2-4 interact with the haem group). Four iterations on SPTR55_38f were required to reach convergence, at which point a true set comprising 101 sequences was identified. Eight partial matches were also found, all of which are family members that fail to make signficant matches with one or more motifs.

References

1.Functioning haemoglobin genes in non-nodulating plants. Bogusz D, Appleby CA, Landsmann J, Dennis ES, Trinick MJ, Peacock WJ. Nature 331, 178-80, (1988). View articlePMID: 2448639

2.Structure of leghaemoglobin from lupin root nodules at 5 angstrom resolution. Vainshtein BK, Harutyunyan EH, Kuranova IP, Borisov VV, Sosfenov NI, Pavlovsky AG, Grebenko AI, Konareva NV. Nature 254, 163-4, (1975). View articlePMID: 1118009

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