» Articles » PMID: 10986467

Crystal Structure of a Nonsymbiotic Plant Hemoglobin

Overview
Journal Structure
Publisher Cell Press
Date 2000 Sep 15
PMID 10986467
Citations 39
Authors
Affiliations
Soon will be listed here.
Abstract

Background: Nonsymbiotic hemoglobins (nsHbs) form a new class of plant proteins that is distinct genetically and structurally from leghemoglobins. They are found ubiquitously in plants and are expressed in low concentrations in a variety of tissues including roots and leaves. Their function involves a biochemical response to growth under limited O(2) conditions.

Results: The first X-ray crystal structure of a member of this class of proteins, riceHb1, has been determined to 2.4 A resolution using a combination of phasing techniques. The active site of ferric riceHb1 differs significantly from those of traditional hemoglobins and myoglobins. The proximal and distal histidine sidechains coordinate directly to the heme iron, forming a hemichrome with spectral properties similar to those of cytochrome b(5). The crystal structure also shows that riceHb1 is a dimer with a novel interface formed by close contacts between the G helix and the region between the B and C helices of the partner subunit.

Conclusions: The bis-histidyl heme coordination found in riceHb1 is unusual for a protein that binds O(2) reversibly. However, the distal His73 is rapidly displaced by ferrous ligands, and the overall O(2) affinity is ultra-high (K(D) approximately 1 nM). Our crystallographic model suggests that ligand binding occurs by an upward and outward movement of the E helix, concomitant dissociation of the distal histidine, possible repacking of the CD corner and folding of the D helix. Although the functional relevance of quaternary structure in nsHbs is unclear, the role of two conserved residues in stabilizing the dimer interface has been identified.

Citing Articles

Conformational Dynamics of Phytoglobin BvPgb1.2 from ssp. .

Christensen S, Stenstrom O, Akke M, Bulow L Int J Mol Sci. 2023; 24(4).

PMID: 36835381 PMC: 9961634. DOI: 10.3390/ijms24043973.


Oxidative Implications of Substituting a Conserved Cysteine Residue in Sugar Beet Phytoglobin BvPgb 1.2.

Christensen S, Groth L, Leiva-Eriksson N, Nyblom M, Bulow L Antioxidants (Basel). 2022; 11(8).

PMID: 36009334 PMC: 9404779. DOI: 10.3390/antiox11081615.


Sugar beet hemoglobins: reactions with nitric oxide and nitrite reveal differential roles for nitrogen metabolism.

Leiva Eriksson N, Reeder B, Wilson M, Bulow L Biochem J. 2019; 476(14):2111-2125.

PMID: 31285352 PMC: 6668756. DOI: 10.1042/BCJ20190154.


Phytoglobin overexpression promotes barley growth in the presence of enhanced level of atmospheric nitric oxide.

Zhang J, Buegger F, Albert A, Ghirardo A, Winkler B, Schnitzler J J Exp Bot. 2019; 70(17):4521-4537.

PMID: 31245808 PMC: 6736386. DOI: 10.1093/jxb/erz249.


Residues in the Distal Heme Pocket of Arabidopsis Non-Symbiotic Hemoglobins: Implication for Nitrite Reductase Activity.

Kumar N, Astegno A, Chen J, Giorgetti A, Dominici P Int J Mol Sci. 2016; 17(5).

PMID: 27136534 PMC: 4881466. DOI: 10.3390/ijms17050640.