Ferredoxin: Difference between revisions
Michal Harel (talk | contribs) No edit summary |
No edit summary |
||
| Line 19: | Line 19: | ||
==ISC-like [2Fe-2S] ferredoxin (FdxB) dimer from ''Pseudomonas putida'' JCM 20004<ref>DOI:10.1007/s00775-011-0793-8</ref>== | ==ISC-like [2Fe-2S] ferredoxin (FdxB) dimer from ''Pseudomonas putida'' JCM 20004<ref>DOI:10.1007/s00775-011-0793-8</ref>== | ||
Biological iron-sulfur (Fe-S) clusters are functionally versatile, modular prosthetic groups. The electronic structure and the site of iron reduction of these protein-bound cofactors account for the electron transfer function and mechanism. In the present work we have solved the structure of the ISC-like [2Fe-2S] ferredoxin called FdxB from the non-pathogenic gammaproteobacterium ''Pseudomonas putida'' JCM 20004 (formerly ''Pseudomonas ovalis'' IAM 1002). This FdxB protein contains an adrenodoxin (Adx) like, redox-active [2Fe-2S] cluster, which plays an essential role in the de novo iron-sulfur cluster assembly (ISC) system. It is encoded by the fdxB gene as a constituent of the cognate iscR-iscS1-iscU-iscA-hscB-hscA-fdxB gene cluster for the ISC system (DDBJ-EMBL-GenBank code AB109467). In ''P. putida'' the ISC pathway is apparently the sole system for ''in vivo'' Fe-S cluster assembly whereas the SUF pathway is missing in the bacterial genome (unlike in ''Escherichia coli''). | Biological iron-sulfur (Fe-S) clusters are functionally versatile, modular prosthetic groups. The electronic structure and the site of iron reduction of these protein-bound cofactors account for the electron transfer function and mechanism. In the present work we have solved the structure of the ISC-like [2Fe-2S] ferredoxin called FdxB from the non-pathogenic gammaproteobacterium ''Pseudomonas putida'' JCM 20004 (formerly ''Pseudomonas ovalis'' IAM 1002) ([[3ah7]]). This FdxB protein contains an adrenodoxin (Adx) like, redox-active [2Fe-2S] cluster, which plays an essential role in the de novo iron-sulfur cluster assembly (ISC) system. It is encoded by the fdxB gene as a constituent of the cognate iscR-iscS1-iscU-iscA-hscB-hscA-fdxB gene cluster for the ISC system (DDBJ-EMBL-GenBank code AB109467). In ''P. putida'' the ISC pathway is apparently the sole system for ''in vivo'' Fe-S cluster assembly whereas the SUF pathway is missing in the bacterial genome (unlike in ''Escherichia coli''). | ||
The <scene name='Journal:JBIC:12/Cv1/1'>FdxB structure</scene> has a βαββαβ fold with the β-grasp/ubiquitin-like fold motif as found in regular eukaryal and bacterial [2Fe-2S] ferredoxins (e.g. [[1i7h]], [[1cje]], [[1e9m]]). FdxB is folded into an (α+β) <scene name='Journal:JBIC:12/Cv1/2'>core fold domain and an extended C-terminal tail</scene>. In the lattice <scene name='Journal:JBIC:12/Cv1/3'>FdxB was found to be homo-dimeric, </scene> displaying the <scene name='Journal:JBIC:12/Cv1/13'>isologous association of the extended C-terminal tail from each protomer</scene>. Each protomer binds a <scene name='Journal:JBIC:12/Cv1/4'>[2Fe-2S] cluster</scene> that is <scene name='Journal:JBIC:12/Cv1/5'>coordinated by four terminal cysteine sulfur atoms</scene>, where the <scene name='Journal:JBIC:12/Cv1/7'>outermost iron (Fe1) near the protein surface is coordinated by Cys41S and Cys47S</scene> and the <scene name='Journal:JBIC:12/Cv1/8'>innermost iron (Fe2) by Cys50S and Cys86S</scene>. In the <scene name='Journal:JBIC:12/Cv1/9'>dimeric structure, two [2Fe-2S] clusters are separated at the closest iron-to-iron (Fe1-Fe1) distance of 25 A</scene>, suggesting that a rapid interprotomer electron transfer between them would be unlikely to occur. In the place of the consensus free cysteine usually present near the [2Fe-2S] cluster of ISC-like ferredoxins, FdxB has the <scene name='Journal:JBIC:12/Cv1/10'>Lys45 side chain which forms a salt-bridge interaction with Asp65</scene> Oδ2. Thus, the overall FdxB structural features argue for its primarily electron transfer role in the cognate ISC system, rather than the direct catalytic function. | The <scene name='Journal:JBIC:12/Cv1/1'>FdxB structure</scene> has a βαββαβ fold with the β-grasp/ubiquitin-like fold motif as found in regular eukaryal and bacterial [2Fe-2S] ferredoxins (e.g. [[1i7h]], [[1cje]], [[1e9m]]). FdxB is folded into an (α+β) <scene name='Journal:JBIC:12/Cv1/2'>core fold domain and an extended C-terminal tail</scene>. In the lattice <scene name='Journal:JBIC:12/Cv1/3'>FdxB was found to be homo-dimeric, </scene> displaying the <scene name='Journal:JBIC:12/Cv1/13'>isologous association of the extended C-terminal tail from each protomer</scene>. Each protomer binds a <scene name='Journal:JBIC:12/Cv1/4'>[2Fe-2S] cluster</scene> that is <scene name='Journal:JBIC:12/Cv1/5'>coordinated by four terminal cysteine sulfur atoms</scene>, where the <scene name='Journal:JBIC:12/Cv1/7'>outermost iron (Fe1) near the protein surface is coordinated by Cys41S and Cys47S</scene> and the <scene name='Journal:JBIC:12/Cv1/8'>innermost iron (Fe2) by Cys50S and Cys86S</scene>. In the <scene name='Journal:JBIC:12/Cv1/9'>dimeric structure, two [2Fe-2S] clusters are separated at the closest iron-to-iron (Fe1-Fe1) distance of 25 A</scene>, suggesting that a rapid interprotomer electron transfer between them would be unlikely to occur. In the place of the consensus free cysteine usually present near the [2Fe-2S] cluster of ISC-like ferredoxins, FdxB has the <scene name='Journal:JBIC:12/Cv1/10'>Lys45 side chain which forms a salt-bridge interaction with Asp65</scene> Oδ2. Thus, the overall FdxB structural features argue for its primarily electron transfer role in the cognate ISC system, rather than the direct catalytic function. | ||