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Comparative Study
. 2001 Aug 28;98(18):10119-24.
doi: 10.1073/pnas.191349198.

A hemoglobin from plants homologous to truncated hemoglobins of microorganisms

R A Watts  1 , P W Hunt, A N Hvitved, M S Hargrove, W J Peacock, E S Dennis
Affiliations
Comparative Study

A hemoglobin from plants homologous to truncated hemoglobins of microorganisms

R A Watts et al. Proc Natl Acad Sci U S A. .

Abstract

We have identified a nuclear-encoded Hb from plants (GLB3) that has a central domain similar to the "truncated" Hbs of bacteria, protozoa, and algae. The three-dimensional structure of these Hbs is a 2-on-2 arrangement of alpha-helices, distinct from the 3-on-3 arrangement of the standard globin fold [Pesce, A., Couture, M., Dewilde, S., Guertin, M., Yamauchi, K., Ascenzi, P., Moens, L. & Bolognesi, M. (2000) EMBO J. 19, 2424-2434]. GLB3-like genes are not found in animals or yeast, but our analysis reveals that they are present in a wide range of Angiosperms and a Bryophyte. Although cyanobacteria and Chlamydomonas have 2-on-2 Hbs (GLBN), GLB3 is more likely related to GLBO-type 2-on-2 Hbs from bacteria. Consequently, GLB3 is unlikely to have arisen from a horizontal transfer between the chloroplast and nuclear genomes. Arabidopsis thaliana GLB3 protein exhibits unusual concentration-independent binding of O(2) and CO. The absorbance spectrum of deoxy-GLB3 is unique; the protein forms a transient six-coordinate structure after reduction and deoxygenation, which slowly converts to a five-coordinate structure. In A. thaliana, GLB3 is expressed throughout the plant but responds to none of the treatments that induce plant 3-on-3 Hbs. Our analysis of the sequence, ligand interactions, and expression profile of GLB3 indicates that this protein has unique biochemical properties, evolutionary history, and, most likely, a function distinct from those of other plant Hbs.

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Figures

Figure 1
Figure 1
The N- and C-terminal domains of some plant GLB3 proteins are shown in A, with a portion of the central region connecting them aligned with other Hbs in B. In A, the full C-terminal portion of cotton GLB3 is not shown, as it has not been determined. Shown in B is a structure-based sequence alignment of plant GLB3 proteins from A. thaliana, barley, barrel medic, and cotton, with 2-on-2 Hbs from microorganisms (2) and plant Hbs that have a myoglobin-like fold (11). Boxed regions denote α-helical regions in the structures of rice GLB1;1 and the 2-on-2 Hb of P. caudatum. Residues conserved between M. tuberculosis GLBO and GLB3 proteins are highlighted. The proximal (F8) and distal (E7) residues are marked with a star, and the helix designations for the beginning and end of the central domain are given.
Figure 2
Figure 2
(A) Consensus tree showing the relationships among Hbs using minimum evolution. (B) An alternative arrangement of 2-on-2 Hb clades, found by using maximum parsimony. Bootstrap scores are indicated above the line for important clades; some scores have been omitted for clarity of presentation. See supplemental data for more details (www.pnas.org).
Figure 3
Figure 3
Northern blot analysis of ARAth GLB3 expression in A. thaliana. Lanes contain 25 μg of RNA from (Lane 1) roots, (Lane 2) leaves, and hypocotyl, (Lane 3) whole plants, (Lane 4) ABA, (Lane 5) 2,4-D, (Lane 6) 2iP, and (Lane 7) hypoxia-treated whole plants.
Figure 4
Figure 4
The absorption spectra of A. thaliana GLB3 are shown (A). The absorption spectra of deoxyferrous GLB3 (solid line), O2-GLB3 (dashed), CO-GLB3 (dot-dash), and ferricGLB3 (dotted) are shown. The change in spectrum of deoxy-GLB3 over time is depicted (B), with the time dependence of the decay from six- to five-coordinate shown (Inset).
Figure 5
Figure 5
Concentration dependence of CO and O2 binding to A. thaliana GLB3 after rapid mixing (A). Concentration dependence of CO binding to soybean GLB2S;a (B) and A. thaliana GLB3 (C), after flash photolysis.
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References

    1. Bashford D, Chothia C, Lesk A M. J Mol Biol. 1987;196:199–216. - PubMed
    1. Pesce A, Couture M, Dewilde S, Guertin M, Yamauchi K, Ascenzi P, Moens L, Bolognesi M. EMBO J. 2000;19:2424–2434. - PMC - PubMed
    1. Moens L, Vanfleteren J, Van de Peer Y, Peeters K, Kapp O, Czeluzniak J, Goodman M, Blaxter M, Vinogradov S. Mol Biol Evol. 1996;13:324–333. - PubMed
    1. Suzuki T, Imai K. Cell Mol Life Sci. 1998;54:979–1004. - PMC - PubMed
    1. Altschul S F, Madden T L, Schäffer A A, Zhang J, Zhang Z, Miller W, Lipman D J. Nucleic Acids Res. 1997;25:3389–3402. - PMC - PubMed

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