Maturation of Plastid c-type Cytochromes
Cytochromes c are hemoproteins, with the prosthetic group covalently linked to the apoprotein, which function as electron carriers. A class of cytochromes c is defined by a CXXCH heme-binding motif where the cysteines form thioether bonds with the vinyl groups of heme. Plastids are known to contain...
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| Format: | Article |
| Language: | English |
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Frontiers Media S.A.
2017-07-01
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| Series: | Frontiers in Plant Science |
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| Online Access: | http://journal.frontiersin.org/article/10.3389/fpls.2017.01313/full |
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| author | Stéphane T. Gabilly Stéphane T. Gabilly Patrice P. Hamel Patrice P. Hamel |
| author_facet | Stéphane T. Gabilly Stéphane T. Gabilly Patrice P. Hamel Patrice P. Hamel |
| author_sort | Stéphane T. Gabilly |
| collection | DOAJ |
| description | Cytochromes c are hemoproteins, with the prosthetic group covalently linked to the apoprotein, which function as electron carriers. A class of cytochromes c is defined by a CXXCH heme-binding motif where the cysteines form thioether bonds with the vinyl groups of heme. Plastids are known to contain up to three cytochromes c. The membrane-bound cytochrome f and soluble cytochrome c6 operate in photosynthesis while the activity of soluble cytochrome c6A remains unknown. Conversion of apo- to holocytochrome c occurs in the thylakoid lumen and requires the independent transport of apocytochrome and heme across the thylakoid membrane followed by the stereospecific attachment of ferroheme via thioether linkages. Attachment of heme to apoforms of plastid cytochromes c is dependent upon the products of the CCS (for cytochrome csynthesis) genes, first uncovered via genetic analysis of photosynthetic deficient mutants in the green alga Chlamydomonas reinhardtii. The CCS pathway also occurs in cyanobacteria and several bacteria. CcsA and CCS1, the signature components of the CCS pathway are polytopic membrane proteins proposed to operate in the delivery of heme from the stroma to the lumen, and also in the catalysis of the heme ligation reaction. CCDA, CCS4, and CCS5 are components of trans-thylakoid pathways that deliver reducing equivalents in order to maintain the heme-binding cysteines in a reduced form prior to thioether bond formation. While only four CCS components are needed in bacteria, at least eight components are required for plastid cytochrome c assembly, suggesting the biochemistry of thioether formation is more nuanced in the plastid system. |
| first_indexed | 2024-12-11T03:03:16Z |
| format | Article |
| id | doaj.art-a20b88d8a98a40eb93ca3392aeeaf36e |
| institution | Directory Open Access Journal |
| issn | 1664-462X |
| language | English |
| last_indexed | 2024-12-11T03:03:16Z |
| publishDate | 2017-07-01 |
| publisher | Frontiers Media S.A. |
| record_format | Article |
| series | Frontiers in Plant Science |
| spelling | doaj.art-a20b88d8a98a40eb93ca3392aeeaf36e2022-12-22T01:23:00ZengFrontiers Media S.A.Frontiers in Plant Science1664-462X2017-07-01810.3389/fpls.2017.01313274008Maturation of Plastid c-type CytochromesStéphane T. Gabilly0Stéphane T. Gabilly1Patrice P. Hamel2Patrice P. Hamel3Department of Molecular Genetics and Department of Biological Chemistry and Pharmacology, The Ohio State University, ColumbusOH, United StatesMolecular and Cellular Developmental Biology Graduate Program, The Ohio State University, ColumbusOH, United StatesDepartment of Molecular Genetics and Department of Biological Chemistry and Pharmacology, The Ohio State University, ColumbusOH, United StatesMolecular and Cellular Developmental Biology Graduate Program, The Ohio State University, ColumbusOH, United StatesCytochromes c are hemoproteins, with the prosthetic group covalently linked to the apoprotein, which function as electron carriers. A class of cytochromes c is defined by a CXXCH heme-binding motif where the cysteines form thioether bonds with the vinyl groups of heme. Plastids are known to contain up to three cytochromes c. The membrane-bound cytochrome f and soluble cytochrome c6 operate in photosynthesis while the activity of soluble cytochrome c6A remains unknown. Conversion of apo- to holocytochrome c occurs in the thylakoid lumen and requires the independent transport of apocytochrome and heme across the thylakoid membrane followed by the stereospecific attachment of ferroheme via thioether linkages. Attachment of heme to apoforms of plastid cytochromes c is dependent upon the products of the CCS (for cytochrome csynthesis) genes, first uncovered via genetic analysis of photosynthetic deficient mutants in the green alga Chlamydomonas reinhardtii. The CCS pathway also occurs in cyanobacteria and several bacteria. CcsA and CCS1, the signature components of the CCS pathway are polytopic membrane proteins proposed to operate in the delivery of heme from the stroma to the lumen, and also in the catalysis of the heme ligation reaction. CCDA, CCS4, and CCS5 are components of trans-thylakoid pathways that deliver reducing equivalents in order to maintain the heme-binding cysteines in a reduced form prior to thioether bond formation. While only four CCS components are needed in bacteria, at least eight components are required for plastid cytochrome c assembly, suggesting the biochemistry of thioether formation is more nuanced in the plastid system.http://journal.frontiersin.org/article/10.3389/fpls.2017.01313/fullthylakoid lumenphotosynthesiscytochrome chemethioethercytochrome b6f |
| spellingShingle | Stéphane T. Gabilly Stéphane T. Gabilly Patrice P. Hamel Patrice P. Hamel Maturation of Plastid c-type Cytochromes Frontiers in Plant Science thylakoid lumen photosynthesis cytochrome c heme thioether cytochrome b6f |
| title | Maturation of Plastid c-type Cytochromes |
| title_full | Maturation of Plastid c-type Cytochromes |
| title_fullStr | Maturation of Plastid c-type Cytochromes |
| title_full_unstemmed | Maturation of Plastid c-type Cytochromes |
| title_short | Maturation of Plastid c-type Cytochromes |
| title_sort | maturation of plastid c type cytochromes |
| topic | thylakoid lumen photosynthesis cytochrome c heme thioether cytochrome b6f |
| url | http://journal.frontiersin.org/article/10.3389/fpls.2017.01313/full |
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