{"id":{"repo_id":"uiuc","oai_identifier":"oai:www.ideals.illinois.edu:2142/77664"},"canonical_url":"https://search.dev.ndltd.org/etd/uiuc/oai:www.ideals.illinois.edu:2142/77664","repository":{"repo_id":"uiuc","name":"University of Illinois - Urbana-Champaign","base_url":"https://www.ideals.illinois.edu/oai-pmh"},"display":{"title":"The Mechanism of Bicarbonate Activation of Plastoquinone Reduction in Photosystem II of Photosynthesis","abstract":"Bicarbonate (HCO$\\sb{3}\\sp{-}$) is required for photosystem II (PS II) electron transport. Depleting thylakoids of HCO$\\sb{3}\\sp{-}$ slows down electron transfer from the primary quinone acceptor Q$\\sb{\\rm A}$ to the secondary quinone acceptor Q$\\sb{\\rm B}$. It also blocks electron transfer from Q$\\sb{\\rm B}$ to the plastoquinone (PQ) pool. This effect is reversible, and is specific for HCO$\\sb{3}\\sp{-}$. A variety of biochemical and biophysical methods were used to probe the mechanism of this requirement. The chemical species required is HCO$\\sb{3}\\sp{-}$, not CO$\\sb2$, H$\\sb2$CO$\\sb3$ or CO$\\sb{3}\\sp{2-}$: over the pH range of 6.3 to 6.9, the rate of electron flow in HCO$\\sb{3}\\sp{-}$ depleted thylakoids increases in proportion to the equilibrium (HCO$\\sb{3}\\sp{-}$), but is independent of the equilibrium (CO$\\sb2$), (H$\\sb2$CO$\\sb3$), or (CO$\\sb{3}\\sp{2-}$). A kinetic analysis of the Hill activity as a function of the equilibrium (HCO$\\sb{3}\\sp{-}$) indicates that there are at least two sites of HCO$\\sb{3}\\sp{-}$ binding, if it is assumed that the basal activity in the absence of added HCO$\\sb{3}\\sp{-}$ is due to endogenous HCO$\\sb{3}\\sp{-}$. In thylakoids in which all but 7% of the Hill activity was reversibly inhibited by HCO$\\sb{3}\\sp{-}$ depletion, the activity as a function of chlorophyll (Chl) concentration was nonlinear, indicating the presence of endogenous HCO$\\sb{3}\\sp{-}$. When the endogenous HCO$\\sb{3}\\sp{-}$ is included in the total (HCO$\\sb{3}\\sp{-}$), the kinetics are those of a two-site system with high cooperativity between the binding sites. An analog of PQ, containing an azido group capable of photoaffinity attachment, was used to probe whether quinone binding at the Q$\\sb{\\rm B}$ site is affected by HCO$\\sb{3}\\sp{-}$ removal. Less of the analog appears to be able to label the Q$\\sb{\\rm B}$ site when HCO$\\sb{3}\\sp{-}$ is removed, than when it is present, suggesting that the quinone binds less tightly in the absence of HCO$\\sb{3}\\sp{-}$. The PQ analog appeared to be able to oxidize Q$\\sb{\\rm A}\\sp{-}$ directly, and may also impair electron flow from pheophytin (Pheo) to Q$\\sb{\\rm A}$. These latter effects are more pronounced when HCO$\\sb{3}\\sp{-}$ is removed and may be due to conformational changes induced by the removal of HCO$\\sb{3}\\sp{-}$. A model was developed to explain HCO$\\sb{3}\\sp{-}$ action, in which one HCO$\\sb{3}\\sp{-}$ forms a salt bridge between the non-heme Fe$\\sp{2+}$ in PS II and a histadine protein residue, another HCO$\\sb{3}\\sp{-}$ is involved in protonating a histidine near the Q$\\sb{\\rm B}$ site to stabilize Q$\\sb{\\rm B}\\sp{-}$, and a low affinity pool of HCO$\\sb{3}\\sp{-}$ keeps the (HCO$\\sb{3}\\sp{-}$) high in the vicinity of the binding sites.","abstract_html":"Bicarbonate (HCO$\\sb{3}\\sp{-}$) is required for photosystem II (PS II) electron transport. Depleting thylakoids of HCO$\\sb{3}\\sp{-}$ slows down electron transfer from the primary quinone acceptor Q$\\sb{\\rm A}$ to the secondary quinone acceptor Q$\\sb{\\rm B}$. It also blocks electron transfer from Q$\\sb{\\rm B}$ to the plastoquinone (PQ) pool. This effect is reversible, and is specific for HCO$\\sb{3}\\sp{-}$. A variety of biochemical and biophysical methods were used to probe the mechanism of this requirement. The chemical species required is HCO$\\sb{3}\\sp{-}$, not CO$\\sb2$, H$\\sb2$CO$\\sb3$ or CO$\\sb{3}\\sp{2-}$: over the pH range of 6.3 to 6.9, the rate of electron flow in HCO$\\sb{3}\\sp{-}$ depleted thylakoids increases in proportion to the equilibrium (HCO$\\sb{3}\\sp{-}$), but is independent of the equilibrium (CO$\\sb2$), (H$\\sb2$CO$\\sb3$), or (CO$\\sb{3}\\sp{2-}$). A kinetic analysis of the Hill activity as a function of the equilibrium (HCO$\\sb{3}\\sp{-}$) indicates that there are at least two sites of HCO$\\sb{3}\\sp{-}$ binding, if it is assumed that the basal activity in the absence of added HCO$\\sb{3}\\sp{-}$ is due to endogenous HCO$\\sb{3}\\sp{-}$. In thylakoids in which all but 7% of the Hill activity was reversibly inhibited by HCO$\\sb{3}\\sp{-}$ depletion, the activity as a function of chlorophyll (Chl) concentration was nonlinear, indicating the presence of endogenous HCO$\\sb{3}\\sp{-}$. When the endogenous HCO$\\sb{3}\\sp{-}$ is included in the total (HCO$\\sb{3}\\sp{-}$), the kinetics are those of a two-site system with high cooperativity between the binding sites. An analog of PQ, containing an azido group capable of photoaffinity attachment, was used to probe whether quinone binding at the Q$\\sb{\\rm B}$ site is affected by HCO$\\sb{3}\\sp{-}$ removal. Less of the analog appears to be able to label the Q$\\sb{\\rm B}$ site when HCO$\\sb{3}\\sp{-}$ is removed, than when it is present, suggesting that the quinone binds less tightly in the absence of HCO$\\sb{3}\\sp{-}$. The PQ analog appeared to be able to oxidize Q$\\sb{\\rm A}\\sp{-}$ directly, and may also impair electron flow from pheophytin (Pheo) to Q$\\sb{\\rm A}$. These latter effects are more pronounced when HCO$\\sb{3}\\sp{-}$ is removed and may be due to conformational changes induced by the removal of HCO$\\sb{3}\\sp{-}$. A model was developed to explain HCO$\\sb{3}\\sp{-}$ action, in which one HCO$\\sb{3}\\sp{-}$ forms a salt bridge between the non-heme Fe$\\sp{2+}$ in PS II and a histadine protein residue, another HCO$\\sb{3}\\sp{-}$ is involved in protonating a histidine near the Q$\\sb{\\rm B}$ site to stabilize Q$\\sb{\\rm B}\\sp{-}$, and a low affinity pool of HCO$\\sb{3}\\sp{-}$ keeps the (HCO$\\sb{3}\\sp{-}$) high in the vicinity of the binding sites.","abstract_has_math":true,"creators":["Blubaugh, Danny J."],"institution":"University of Illinois at Urbana-Champaign","degree_name":"Ph.D.","degree_level":"Dissertation","degree_discipline":"Botany","degree_department":null,"school":null,"contributors":[],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2015,"date_issued":"2015-05-14T15:19:17Z","date_published":"2015-05-14T15:19:17Z","updated_at":"2026-07-22T22:26:11Z","subjects":["Biology, Plant Physiology"],"languages":["eng"],"rights":[],"rights_urls":[],"identifier_entries":[{"key":"dc:identifier","label":"Identifier","values":["(UMI)AAI8802984"],"render_values":[{"text":"(UMI)AAI8802984","href":null,"code":true}]}]},"links":{"outbound_url":"http://hdl.handle.net/2142/77664","outbound_label":"Handle","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:creator","label":"Author","values":["Blubaugh, Danny J."]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2015-05-14T15:19:17Z","10000-01-01","1987"]},{"key":"dc:type","label":"Dc Type","values":["text"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Botany"]},{"key":"thesis:degree_level","label":"Degree Level","values":["Dissertation"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Ph.D."]},{"key":"thesis:institution_name","label":"Thesis Institution Name","values":["University of Illinois at Urbana-Champaign"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Biology, Plant Physiology"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["eng"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["http://hdl.handle.net/2142/77664","(UMI)AAI8802984"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["Bicarbonate (HCO$\\sb{3}\\sp{-}$) is required for photosystem II (PS II) electron transport. Depleting thylakoids of HCO$\\sb{3}\\sp{-}$ slows down electron transfer from the primary quinone acceptor Q$\\sb{\\rm A}$ to the secondary quinone acceptor Q$\\sb{\\rm B}$. It also blocks electron transfer from Q$\\sb{\\rm B}$ to the plastoquinone (PQ) pool. This effect is reversible, and is specific for HCO$\\sb{3}\\sp{-}$. A variety of biochemical and biophysical methods were used to probe the mechanism of this requirement. The chemical species required is HCO$\\sb{3}\\sp{-}$, not CO$\\sb2$, H$\\sb2$CO$\\sb3$ or CO$\\sb{3}\\sp{2-}$: over the pH range of 6.3 to 6.9, the rate of electron flow in HCO$\\sb{3}\\sp{-}$ depleted thylakoids increases in proportion to the equilibrium (HCO$\\sb{3}\\sp{-}$), but is independent of the equilibrium (CO$\\sb2$), (H$\\sb2$CO$\\sb3$), or (CO$\\sb{3}\\sp{2-}$). A kinetic analysis of the Hill activity as a function of the equilibrium (HCO$\\sb{3}\\sp{-}$) indicates that there are at least two sites of HCO$\\sb{3}\\sp{-}$ binding, if it is assumed that the basal activity in the absence of added HCO$\\sb{3}\\sp{-}$ is due to endogenous HCO$\\sb{3}\\sp{-}$. In thylakoids in which all but 7% of the Hill activity was reversibly inhibited by HCO$\\sb{3}\\sp{-}$ depletion, the activity as a function of chlorophyll (Chl) concentration was nonlinear, indicating the presence of endogenous HCO$\\sb{3}\\sp{-}$. When the endogenous HCO$\\sb{3}\\sp{-}$ is included in the total (HCO$\\sb{3}\\sp{-}$), the kinetics are those of a two-site system with high cooperativity between the binding sites. An analog of PQ, containing an azido group capable of photoaffinity attachment, was used to probe whether quinone binding at the Q$\\sb{\\rm B}$ site is affected by HCO$\\sb{3}\\sp{-}$ removal. Less of the analog appears to be able to label the Q$\\sb{\\rm B}$ site when HCO$\\sb{3}\\sp{-}$ is removed, than when it is present, suggesting that the quinone binds less tightly in the absence of HCO$\\sb{3}\\sp{-}$. The PQ analog appeared to be able to oxidize Q$\\sb{\\rm A}\\sp{-}$ directly, and may also impair electron flow from pheophytin (Pheo) to Q$\\sb{\\rm A}$. These latter effects are more pronounced when HCO$\\sb{3}\\sp{-}$ is removed and may be due to conformational changes induced by the removal of HCO$\\sb{3}\\sp{-}$. A model was developed to explain HCO$\\sb{3}\\sp{-}$ action, in which one HCO$\\sb{3}\\sp{-}$ forms a salt bridge between the non-heme Fe$\\sp{2+}$ in PS II and a histadine protein residue, another HCO$\\sb{3}\\sp{-}$ is involved in protonating a histidine near the Q$\\sb{\\rm B}$ site to stabilize Q$\\sb{\\rm B}\\sp{-}$, and a low affinity pool of HCO$\\sb{3}\\sp{-}$ keeps the (HCO$\\sb{3}\\sp{-}$) high in the vicinity of the binding sites.","Made available in DSpace on 2015-05-14T15:19:17Z (GMT). No. of bitstreams: 2 license.txt: 4848 bytes, checksum: 96035ab3f5e1c23cc7138a224ce498bd (MD5) 8802984.PDF: 8063426 bytes, checksum: 1261bd1409ae171e83654d4cfc7e33b0 (MD5) Previous issue date: 1987","Embargo set by: Seth Robbins for item 78874 Lift date: Forever Reason: Restricted to the U of I community idenfinitely during batch ingest of legacy ETDs","Restricted to the U of I community idenfinitely during batch ingest of legacy ETDs","U of I Only","240 p.","Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1987."]},{"key":"dc:title","label":"Title","values":["The Mechanism of Bicarbonate Activation of Plastoquinone Reduction in Photosystem II of Photosynthesis"]}]}],"canonical_facts":{"dc:creator":["Blubaugh, Danny J."],"dc:date":["2015-05-14T15:19:17Z","10000-01-01","1987"],"dc:description":["Bicarbonate (HCO$\\sb{3}\\sp{-}$) is required for photosystem II (PS II) electron transport. Depleting thylakoids of HCO$\\sb{3}\\sp{-}$ slows down electron transfer from the primary quinone acceptor Q$\\sb{\\rm A}$ to the secondary quinone acceptor Q$\\sb{\\rm B}$. It also blocks electron transfer from Q$\\sb{\\rm B}$ to the plastoquinone (PQ) pool. This effect is reversible, and is specific for HCO$\\sb{3}\\sp{-}$. A variety of biochemical and biophysical methods were used to probe the mechanism of this requirement. The chemical species required is HCO$\\sb{3}\\sp{-}$, not CO$\\sb2$, H$\\sb2$CO$\\sb3$ or CO$\\sb{3}\\sp{2-}$: over the pH range of 6.3 to 6.9, the rate of electron flow in HCO$\\sb{3}\\sp{-}$ depleted thylakoids increases in proportion to the equilibrium (HCO$\\sb{3}\\sp{-}$), but is independent of the equilibrium (CO$\\sb2$), (H$\\sb2$CO$\\sb3$), or (CO$\\sb{3}\\sp{2-}$). A kinetic analysis of the Hill activity as a function of the equilibrium (HCO$\\sb{3}\\sp{-}$) indicates that there are at least two sites of HCO$\\sb{3}\\sp{-}$ binding, if it is assumed that the basal activity in the absence of added HCO$\\sb{3}\\sp{-}$ is due to endogenous HCO$\\sb{3}\\sp{-}$. In thylakoids in which all but 7% of the Hill activity was reversibly inhibited by HCO$\\sb{3}\\sp{-}$ depletion, the activity as a function of chlorophyll (Chl) concentration was nonlinear, indicating the presence of endogenous HCO$\\sb{3}\\sp{-}$. When the endogenous HCO$\\sb{3}\\sp{-}$ is included in the total (HCO$\\sb{3}\\sp{-}$), the kinetics are those of a two-site system with high cooperativity between the binding sites. An analog of PQ, containing an azido group capable of photoaffinity attachment, was used to probe whether quinone binding at the Q$\\sb{\\rm B}$ site is affected by HCO$\\sb{3}\\sp{-}$ removal. Less of the analog appears to be able to label the Q$\\sb{\\rm B}$ site when HCO$\\sb{3}\\sp{-}$ is removed, than when it is present, suggesting that the quinone binds less tightly in the absence of HCO$\\sb{3}\\sp{-}$. The PQ analog appeared to be able to oxidize Q$\\sb{\\rm A}\\sp{-}$ directly, and may also impair electron flow from pheophytin (Pheo) to Q$\\sb{\\rm A}$. These latter effects are more pronounced when HCO$\\sb{3}\\sp{-}$ is removed and may be due to conformational changes induced by the removal of HCO$\\sb{3}\\sp{-}$. A model was developed to explain HCO$\\sb{3}\\sp{-}$ action, in which one HCO$\\sb{3}\\sp{-}$ forms a salt bridge between the non-heme Fe$\\sp{2+}$ in PS II and a histadine protein residue, another HCO$\\sb{3}\\sp{-}$ is involved in protonating a histidine near the Q$\\sb{\\rm B}$ site to stabilize Q$\\sb{\\rm B}\\sp{-}$, and a low affinity pool of HCO$\\sb{3}\\sp{-}$ keeps the (HCO$\\sb{3}\\sp{-}$) high in the vicinity of the binding sites.","Made available in DSpace on 2015-05-14T15:19:17Z (GMT). No. of bitstreams: 2 license.txt: 4848 bytes, checksum: 96035ab3f5e1c23cc7138a224ce498bd (MD5) 8802984.PDF: 8063426 bytes, checksum: 1261bd1409ae171e83654d4cfc7e33b0 (MD5) Previous issue date: 1987","Embargo set by: Seth Robbins for item 78874 Lift date: Forever Reason: Restricted to the U of I community idenfinitely during batch ingest of legacy ETDs","Restricted to the U of I community idenfinitely during batch ingest of legacy ETDs","U of I Only","240 p.","Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1987."],"dc:identifier":["http://hdl.handle.net/2142/77664","(UMI)AAI8802984"],"dc:language":["eng"],"dc:subject":["Biology, Plant Physiology"],"dc:title":["The Mechanism of Bicarbonate Activation of Plastoquinone Reduction in Photosystem II of Photosynthesis"],"dc:type":["text"],"thesis:degree_discipline":["Botany"],"thesis:degree_level":["Dissertation"],"thesis:degree_name":["Ph.D."],"thesis:institution_name":["University of Illinois at Urbana-Champaign"]},"updated_at":"2026-07-22T22:26:11Z"}