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The molecular basis of heme oxygenase deficiency in the pcd1 mutant of pea

The molecular basis of heme oxygenase deficiency in the pcd1 mutant of pea
The molecular basis of heme oxygenase deficiency in the pcd1 mutant of pea
The pcd1 mutant of pea lacks heme oxygenase (HO) activity required for the synthesis of the phytochrome chromophore and is consequently severely deficient in all responses mediated by the phytochrome family of plant photoreceptors. Here we describe the isolation of the gene encoding pea heme oxygenase 1 (PsHO1) and confirm the presence of a mutation in this gene in the pcd1 mutant. PsHO1 shows a high degree of sequence homology to other higher plant HOs, in particular with those from other legume species. Expression of PsHO1 increased in response to white light, but did not respond strongly to narrow band light treatments. Analysis of the biochemical activity of PsHO1 expressed in Escherichia coli demonstrated requirements for reduced ferredoxin, a secondary reductant such as ascorbate and an iron chelator for maximum enzyme activity. Using the crystal structure data from homologous animal and bacterial HOs we have modelled the structure of PsHO1 and demonstrated a high degree of structural conservation despite limited primary sequence homology. However, the catalytic site of PsHO1 is larger than that of animal HOs indicating that it may accommodate an ascorbate molecule in close proximity to the heme. This could provide an explanation for why plant HOs show a strong and saturable dependence on this reductant.

biliverdin, photomorphogenesis, phytochrome, plastid, structural modelling
1742-464X
2594-2606
Linley, P.J.
31574fdd-77ae-4ed1-af05-0f4bc271424a
Landsberger, M.
27c4f619-cd93-4765-8182-99946b5871a9
Kohchi, T.
4f720505-ce7a-4264-b5b6-d7f7899d256d
Cooper, J.B.
d9f0f6a8-1260-48fc-aa5c-3dbc650e3ec0
Terry, M.J.
a8c2cd6b-8d35-4053-8d77-3841c2427c3b
Linley, P.J.
31574fdd-77ae-4ed1-af05-0f4bc271424a
Landsberger, M.
27c4f619-cd93-4765-8182-99946b5871a9
Kohchi, T.
4f720505-ce7a-4264-b5b6-d7f7899d256d
Cooper, J.B.
d9f0f6a8-1260-48fc-aa5c-3dbc650e3ec0
Terry, M.J.
a8c2cd6b-8d35-4053-8d77-3841c2427c3b

Linley, P.J., Landsberger, M., Kohchi, T., Cooper, J.B. and Terry, M.J. (2006) The molecular basis of heme oxygenase deficiency in the pcd1 mutant of pea. Febs Journal, 273, 2594-2606. (doi:10.1111/j.1742-4658.2006.05264.x).

Record type: Article

Abstract

The pcd1 mutant of pea lacks heme oxygenase (HO) activity required for the synthesis of the phytochrome chromophore and is consequently severely deficient in all responses mediated by the phytochrome family of plant photoreceptors. Here we describe the isolation of the gene encoding pea heme oxygenase 1 (PsHO1) and confirm the presence of a mutation in this gene in the pcd1 mutant. PsHO1 shows a high degree of sequence homology to other higher plant HOs, in particular with those from other legume species. Expression of PsHO1 increased in response to white light, but did not respond strongly to narrow band light treatments. Analysis of the biochemical activity of PsHO1 expressed in Escherichia coli demonstrated requirements for reduced ferredoxin, a secondary reductant such as ascorbate and an iron chelator for maximum enzyme activity. Using the crystal structure data from homologous animal and bacterial HOs we have modelled the structure of PsHO1 and demonstrated a high degree of structural conservation despite limited primary sequence homology. However, the catalytic site of PsHO1 is larger than that of animal HOs indicating that it may accommodate an ascorbate molecule in close proximity to the heme. This could provide an explanation for why plant HOs show a strong and saturable dependence on this reductant.

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More information

Published date: 1 June 2006
Keywords: biliverdin, photomorphogenesis, phytochrome, plastid, structural modelling

Identifiers

Local EPrints ID: 56321
URI: http://eprints.soton.ac.uk/id/eprint/56321
ISSN: 1742-464X
PURE UUID: 66c21055-8e6b-4857-b42c-2127e1f0fd8e
ORCID for M.J. Terry: ORCID iD orcid.org/0000-0001-5002-2708

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Date deposited: 06 Aug 2008
Last modified: 16 Mar 2024 02:52

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Contributors

Author: P.J. Linley
Author: M. Landsberger
Author: T. Kohchi
Author: J.B. Cooper
Author: M.J. Terry ORCID iD

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