{"id":{"repo_id":"vt","oai_identifier":"oai:vtechworks.lib.vt.edu:10919/29255"},"canonical_url":"https://search.dev.ndltd.org/etd/vt/oai:vtechworks.lib.vt.edu:10919/29255","repository":{"repo_id":"vt","name":"Virginia Tech","base_url":"https://vtechworks.lib.vt.edu/oai/request"},"display":{"title":"Molecular biology and biochemical characterization of the CO dehydrogenase-linked ferredoxin from Methanosarcina thermophila strain TM-1","abstract":"The CO dehydrogenase~linked ferredoxin from acetate-grown <i>Methanosarcina thermophiIa</i> was characterized to determine the structure and biochemical properties of the iron-sulfur clusters. Chemical and spectroscopic analyses indicated that the ferredoxin contained two [4Fe-4S] clusters per monomer of 6,790 Da, although a [3Fe-4S] species was also detected in the oxidized protein. The midpoint potentials of the [4Fe-4S] and [3Fe~4S] clusters at pH 7 were -407 m V and + 103 m V, respectively. Evidence from biochemical and spectroscopic studies indicated that the [3Fe-4S] species may have been formed from [4Fe-4S] clusters when ferredoxin was oxidized. The gene encoding the CO dehydrogenase-linked ferredoxin (<i>fdxA</i>) in <i>Ms. thermophila</i> had the coding capacity for a 6,230-Da protein which contained eight cysteines with spacings typical of 2[4Fe-4S] ferredoxins. A second open reading frame (ORF1) was also identified which had the potential to encode a 2[4Fe-4S] bacterial-like ferredoxin (5,850 Da). The deduced proteins from <i>fdxA</i> and ORF1 were 62% identical. <i>fdxA</i> and ORFI were present as single copies in the genome and each was transcribed on a monocistronic mRNA. Both <i>fdxA</i> and ORF1 were transcribed in cells grown on methanol and trimethylamine, but only the <i>fdxA</i> -specific transcript was detected in acetate-grown cells. The apparent transcriptional start sites of <i>fdxA</i> and ORFI were downstream of sequences which had high identity with the consensus methanogen promoter. The heterodisulfide of two cofactors unique to the methanogenic microorganisms, HS-HTP and HS-CoM, was enzymatically reduced in cell extracts of <i>Ms. thermophila</i> using electrons from the oxidation of either H₂ or CO. The homodisulfides of either HS-HTP or HS-CoM were not reduced under the same conditions. The results indicated that methane is formed by reductive demethylation of CH₃-S-CoM using HS-HTP as a reductant in <i>Ms. thermophila</i>. Coupling of CO oxidation with reduction of the heterodisulfide suggested that the CO dehydrogenase-linked ferredoxin may be involved, although the details of electron flow are not known.","abstract_html":"The CO dehydrogenase~linked ferredoxin from acetate-grown &lt;i&gt;Methanosarcina thermophiIa&lt;/i&gt; was characterized to determine the structure and biochemical properties of the iron-sulfur clusters. Chemical and spectroscopic analyses indicated that the ferredoxin contained two [4Fe-4S] clusters per monomer of 6,790 Da, although a [3Fe-4S] species was also detected in the oxidized protein. The midpoint potentials of the [4Fe-4S] and [3Fe~4S] clusters at pH 7 were -407 m V and + 103 m V, respectively. Evidence from biochemical and spectroscopic studies indicated that the [3Fe-4S] species may have been formed from [4Fe-4S] clusters when ferredoxin was oxidized. The gene encoding the CO dehydrogenase-linked ferredoxin (&lt;i&gt;fdxA&lt;/i&gt;) in &lt;i&gt;Ms. thermophila&lt;/i&gt; had the coding capacity for a 6,230-Da protein which contained eight cysteines with spacings typical of 2[4Fe-4S] ferredoxins. A second open reading frame (ORF1) was also identified which had the potential to encode a 2[4Fe-4S] bacterial-like ferredoxin (5,850 Da). The deduced proteins from &lt;i&gt;fdxA&lt;/i&gt; and ORF1 were 62% identical. &lt;i&gt;fdxA&lt;/i&gt; and ORFI were present as single copies in the genome and each was transcribed on a monocistronic mRNA. Both &lt;i&gt;fdxA&lt;/i&gt; and ORF1 were transcribed in cells grown on methanol and trimethylamine, but only the &lt;i&gt;fdxA&lt;/i&gt; -specific transcript was detected in acetate-grown cells. The apparent transcriptional start sites of &lt;i&gt;fdxA&lt;/i&gt; and ORFI were downstream of sequences which had high identity with the consensus methanogen promoter. The heterodisulfide of two cofactors unique to the methanogenic microorganisms, HS-HTP and HS-CoM, was enzymatically reduced in cell extracts of &lt;i&gt;Ms. thermophila&lt;/i&gt; using electrons from the oxidation of either H₂ or CO. The homodisulfides of either HS-HTP or HS-CoM were not reduced under the same conditions. The results indicated that methane is formed by reductive demethylation of CH₃-S-CoM using HS-HTP as a reductant in &lt;i&gt;Ms. thermophila&lt;/i&gt;. Coupling of CO oxidation with reduction of the heterodisulfide suggested that the CO dehydrogenase-linked ferredoxin may be involved, although the details of electron flow are not known.","abstract_has_math":false,"creators":["Clements, Andrew P."],"institution":"Virginia Tech","degree_name":"Ph. D.","degree_level":"doctoral","degree_discipline":"Anaerobic Microbiology","degree_department":"Anaerobic Microbiology","school":null,"contributors":[],"advisors":[],"committee_chairs":["Ferry, James G."],"committee_members":["Dean, Dennis R.","Johnson, John L.","Sitz, Thomas O.","White, Robert H."],"year":1992,"date_issued":"1992-09-05","date_published":"1992-09-05","updated_at":"2026-07-22T22:20:38Z","subjects":[],"languages":["en"],"rights":["In Copyright"],"rights_urls":["http://rightsstatements.org/vocab/InC/1.0/"],"identifier_entries":[{"key":"dc:identifier.other","label":"Dc Identifier Other","values":["etd-10122005-134449"],"render_values":[{"text":"etd-10122005-134449","href":null,"code":true}]}]},"links":{"outbound_url":"http://hdl.handle.net/10919/29255","outbound_label":"Handle","outbound_source":"dc:identifier.uri"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor.committeechair","label":"Committee Chair","values":["Ferry, James G."]},{"key":"dc:contributor.committeemember","label":"Committee Member","values":["Dean, Dennis R.","Johnson, John L.","Sitz, Thomas O.","White, Robert H."]},{"key":"dc:contributor.department","label":"Department","values":["Anaerobic Microbiology"]},{"key":"dc:creator","label":"Author","values":["Clements, Andrew P."]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.accessioned","label":"Dc Date Accessioned","values":["2014-03-14T20:17:19Z"]},{"key":"dc:date.available","label":"Dc Date Available","values":["2014-03-14T20:17:19Z","2012-06-04"]},{"key":"dc:date.issued","label":"Date","values":["1992-09-05"]},{"key":"dc:publisher","label":"Institution","values":["Virginia Tech"]},{"key":"dc:type","label":"Dc Type","values":["Dissertation"]},{"key":"dc:type.dcmitype","label":"Dc Type Dcmitype","values":["Text"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Anaerobic Microbiology"]},{"key":"thesis:degree_level","label":"Degree Level","values":["doctoral"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Ph. 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Chemical and spectroscopic analyses indicated that the ferredoxin contained two [4Fe-4S] clusters per monomer of 6,790 Da, although a [3Fe-4S] species was also detected in the oxidized protein. The midpoint potentials of the [4Fe-4S] and [3Fe~4S] clusters at pH 7 were -407 m V and + 103 m V, respectively. Evidence from biochemical and spectroscopic studies indicated that the [3Fe-4S] species may have been formed from [4Fe-4S] clusters when ferredoxin was oxidized. The gene encoding the CO dehydrogenase-linked ferredoxin (<i>fdxA</i>) in <i>Ms. thermophila</i> had the coding capacity for a 6,230-Da protein which contained eight cysteines with spacings typical of 2[4Fe-4S] ferredoxins. A second open reading frame (ORF1) was also identified which had the potential to encode a 2[4Fe-4S] bacterial-like ferredoxin (5,850 Da). The deduced proteins from <i>fdxA</i> and ORF1 were 62% identical. <i>fdxA</i> and ORFI were present as single copies in the genome and each was transcribed on a monocistronic mRNA. Both <i>fdxA</i> and ORF1 were transcribed in cells grown on methanol and trimethylamine, but only the <i>fdxA</i> -specific transcript was detected in acetate-grown cells. The apparent transcriptional start sites of <i>fdxA</i> and ORFI were downstream of sequences which had high identity with the consensus methanogen promoter. The heterodisulfide of two cofactors unique to the methanogenic microorganisms, HS-HTP and HS-CoM, was enzymatically reduced in cell extracts of <i>Ms. thermophila</i> using electrons from the oxidation of either H₂ or CO. The homodisulfides of either HS-HTP or HS-CoM were not reduced under the same conditions. The results indicated that methane is formed by reductive demethylation of CH₃-S-CoM using HS-HTP as a reductant in <i>Ms. thermophila</i>. Coupling of CO oxidation with reduction of the heterodisulfide suggested that the CO dehydrogenase-linked ferredoxin may be involved, although the details of electron flow are not known."]},{"key":"dc:description.degree","label":"Dc Description Degree","values":["Ph. D."]},{"key":"dc:format.medium","label":"Dc Format Medium","values":["BTD"]},{"key":"dc:format.mimetype","label":"Dc Format Mimetype","values":["application/pdf"]},{"key":"dc:title","label":"Title","values":["Molecular biology and biochemical characterization of the CO dehydrogenase-linked ferredoxin from Methanosarcina thermophila strain TM-1"]}]}],"canonical_facts":{"dc:contributor.committeechair":["Ferry, James G."],"dc:contributor.committeemember":["Dean, Dennis R.","Johnson, John L.","Sitz, Thomas O.","White, Robert H."],"dc:contributor.department":["Anaerobic Microbiology"],"dc:creator":["Clements, Andrew P."],"dc:date.accessioned":["2014-03-14T20:17:19Z"],"dc:date.available":["2014-03-14T20:17:19Z","2012-06-04"],"dc:date.issued":["1992-09-05"],"dc:description.abstract":["The CO dehydrogenase~linked ferredoxin from acetate-grown <i>Methanosarcina thermophiIa</i> was characterized to determine the structure and biochemical properties of the iron-sulfur clusters. Chemical and spectroscopic analyses indicated that the ferredoxin contained two [4Fe-4S] clusters per monomer of 6,790 Da, although a [3Fe-4S] species was also detected in the oxidized protein. The midpoint potentials of the [4Fe-4S] and [3Fe~4S] clusters at pH 7 were -407 m V and + 103 m V, respectively. Evidence from biochemical and spectroscopic studies indicated that the [3Fe-4S] species may have been formed from [4Fe-4S] clusters when ferredoxin was oxidized. The gene encoding the CO dehydrogenase-linked ferredoxin (<i>fdxA</i>) in <i>Ms. thermophila</i> had the coding capacity for a 6,230-Da protein which contained eight cysteines with spacings typical of 2[4Fe-4S] ferredoxins. A second open reading frame (ORF1) was also identified which had the potential to encode a 2[4Fe-4S] bacterial-like ferredoxin (5,850 Da). The deduced proteins from <i>fdxA</i> and ORF1 were 62% identical. <i>fdxA</i> and ORFI were present as single copies in the genome and each was transcribed on a monocistronic mRNA. Both <i>fdxA</i> and ORF1 were transcribed in cells grown on methanol and trimethylamine, but only the <i>fdxA</i> -specific transcript was detected in acetate-grown cells. The apparent transcriptional start sites of <i>fdxA</i> and ORFI were downstream of sequences which had high identity with the consensus methanogen promoter. The heterodisulfide of two cofactors unique to the methanogenic microorganisms, HS-HTP and HS-CoM, was enzymatically reduced in cell extracts of <i>Ms. thermophila</i> using electrons from the oxidation of either H₂ or CO. The homodisulfides of either HS-HTP or HS-CoM were not reduced under the same conditions. The results indicated that methane is formed by reductive demethylation of CH₃-S-CoM using HS-HTP as a reductant in <i>Ms. thermophila</i>. Coupling of CO oxidation with reduction of the heterodisulfide suggested that the CO dehydrogenase-linked ferredoxin may be involved, although the details of electron flow are not known."],"dc:description.degree":["Ph. D."],"dc:format.medium":["BTD"],"dc:format.mimetype":["application/pdf"],"dc:identifier.other":["etd-10122005-134449"],"dc:identifier.uri":["http://hdl.handle.net/10919/29255"],"dc:language.iso":["en"],"dc:publisher":["Virginia Tech"],"dc:rights":["In Copyright"],"dc:rights.uri":["http://rightsstatements.org/vocab/InC/1.0/"],"dc:title":["Molecular biology and biochemical characterization of the CO dehydrogenase-linked ferredoxin from Methanosarcina thermophila strain TM-1"],"dc:type":["Dissertation"],"dc:type.dcmitype":["Text"],"thesis:degree_discipline":["Anaerobic Microbiology"],"thesis:degree_level":["doctoral"],"thesis:degree_name":["Ph. D."],"thesis:institution_name":["Virginia Polytechnic Institute and State University"]},"updated_at":"2026-07-22T22:20:38Z"}