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Structural Determinants of the Outer Shell of β-Carboxysomes in Synechococcus elongatus PCC 7942: Roles for CcmK2, K3-K4, CcmO, and CcmL
Cyanobacterial CO(2)-fixation is supported by a CO(2)-concentrating mechanism which improves photosynthesis by saturating the primary carboxylating enzyme, ribulose 1, 5-bisphosphate carboxylase/oxygenase (RuBisCO), with its preferred substrate CO(2). The site of CO(2)-concentration is a protein bou...
Autores principales: | , , , |
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Formato: | Online Artículo Texto |
Lenguaje: | English |
Publicado: |
Public Library of Science
2012
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Materias: | |
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3425506/ https://www.ncbi.nlm.nih.gov/pubmed/22928045 http://dx.doi.org/10.1371/journal.pone.0043871 |
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author | Rae, Benjamin D. Long, Benedict M. Badger, Murray R. Price, G. Dean |
author_facet | Rae, Benjamin D. Long, Benedict M. Badger, Murray R. Price, G. Dean |
author_sort | Rae, Benjamin D. |
collection | PubMed |
description | Cyanobacterial CO(2)-fixation is supported by a CO(2)-concentrating mechanism which improves photosynthesis by saturating the primary carboxylating enzyme, ribulose 1, 5-bisphosphate carboxylase/oxygenase (RuBisCO), with its preferred substrate CO(2). The site of CO(2)-concentration is a protein bound micro-compartment called the carboxysome which contains most, if not all, of the cellular RuBisCO. The shell of β-type carboxysomes is thought to be composed of two functional layers, with the inner layer involved in RuBisCO scaffolding and bicarbonate dehydration, and the outer layer in selective permeability to dissolved solutes. Here, four genes (ccmK2-4, ccmO), whose products were predicted to function in the outer shell layer of β-carboxysomes from Synechococcus elongatus PCC 7942, were investigated by analysis of defined genetic mutants. Deletion of the ccmK2 and ccmO genes resulted in severe high-CO(2)-requiring mutants with aberrant carboxysomes, whilst deletion of ccmK3 or ccmK4 resulted in cells with wild-type physiology and normal ultrastructure. However, a tandem deletion of ccmK3-4 resulted in cells with wild-type carboxysome structure, but physiologically deficient at low CO(2) conditions. These results revealed the minimum structural determinants of the outer shell of β-carboxysomes from this strain: CcmK2, CcmO and CcmL. An accessory set of proteins was required to refine the function of the pre-existing shell: CcmK3 and CcmK4. These data suggested a model for the facet structure of β-carboxysomes with CcmL forming the vertices, CcmK2 forming the bulk facet, and CcmO, a “zipper protein,” interfacing the edges of carboxysome facets. |
format | Online Article Text |
id | pubmed-3425506 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2012 |
publisher | Public Library of Science |
record_format | MEDLINE/PubMed |
spelling | pubmed-34255062012-08-27 Structural Determinants of the Outer Shell of β-Carboxysomes in Synechococcus elongatus PCC 7942: Roles for CcmK2, K3-K4, CcmO, and CcmL Rae, Benjamin D. Long, Benedict M. Badger, Murray R. Price, G. Dean PLoS One Research Article Cyanobacterial CO(2)-fixation is supported by a CO(2)-concentrating mechanism which improves photosynthesis by saturating the primary carboxylating enzyme, ribulose 1, 5-bisphosphate carboxylase/oxygenase (RuBisCO), with its preferred substrate CO(2). The site of CO(2)-concentration is a protein bound micro-compartment called the carboxysome which contains most, if not all, of the cellular RuBisCO. The shell of β-type carboxysomes is thought to be composed of two functional layers, with the inner layer involved in RuBisCO scaffolding and bicarbonate dehydration, and the outer layer in selective permeability to dissolved solutes. Here, four genes (ccmK2-4, ccmO), whose products were predicted to function in the outer shell layer of β-carboxysomes from Synechococcus elongatus PCC 7942, were investigated by analysis of defined genetic mutants. Deletion of the ccmK2 and ccmO genes resulted in severe high-CO(2)-requiring mutants with aberrant carboxysomes, whilst deletion of ccmK3 or ccmK4 resulted in cells with wild-type physiology and normal ultrastructure. However, a tandem deletion of ccmK3-4 resulted in cells with wild-type carboxysome structure, but physiologically deficient at low CO(2) conditions. These results revealed the minimum structural determinants of the outer shell of β-carboxysomes from this strain: CcmK2, CcmO and CcmL. An accessory set of proteins was required to refine the function of the pre-existing shell: CcmK3 and CcmK4. These data suggested a model for the facet structure of β-carboxysomes with CcmL forming the vertices, CcmK2 forming the bulk facet, and CcmO, a “zipper protein,” interfacing the edges of carboxysome facets. Public Library of Science 2012-08-22 /pmc/articles/PMC3425506/ /pubmed/22928045 http://dx.doi.org/10.1371/journal.pone.0043871 Text en © 2012 Rae et al http://creativecommons.org/licenses/by/4.0/ This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are properly credited. |
spellingShingle | Research Article Rae, Benjamin D. Long, Benedict M. Badger, Murray R. Price, G. Dean Structural Determinants of the Outer Shell of β-Carboxysomes in Synechococcus elongatus PCC 7942: Roles for CcmK2, K3-K4, CcmO, and CcmL |
title | Structural Determinants of the Outer Shell of β-Carboxysomes in Synechococcus elongatus PCC 7942: Roles for CcmK2, K3-K4, CcmO, and CcmL |
title_full | Structural Determinants of the Outer Shell of β-Carboxysomes in Synechococcus elongatus PCC 7942: Roles for CcmK2, K3-K4, CcmO, and CcmL |
title_fullStr | Structural Determinants of the Outer Shell of β-Carboxysomes in Synechococcus elongatus PCC 7942: Roles for CcmK2, K3-K4, CcmO, and CcmL |
title_full_unstemmed | Structural Determinants of the Outer Shell of β-Carboxysomes in Synechococcus elongatus PCC 7942: Roles for CcmK2, K3-K4, CcmO, and CcmL |
title_short | Structural Determinants of the Outer Shell of β-Carboxysomes in Synechococcus elongatus PCC 7942: Roles for CcmK2, K3-K4, CcmO, and CcmL |
title_sort | structural determinants of the outer shell of β-carboxysomes in synechococcus elongatus pcc 7942: roles for ccmk2, k3-k4, ccmo, and ccml |
topic | Research Article |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3425506/ https://www.ncbi.nlm.nih.gov/pubmed/22928045 http://dx.doi.org/10.1371/journal.pone.0043871 |
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