DC Field | Value | Language |
dc.contributor.author | Ahlbrink, R | |
dc.contributor.author | Haumann, M | |
dc.contributor.author | Cherepanov, D | |
dc.contributor.author | Bogershausen, O | |
dc.contributor.author | Mulkidjanian, A | |
dc.contributor.author | Junge, W | |
dc.date.accessioned | 2021-12-23T16:18:09Z | - |
dc.date.available | 2021-12-23T16:18:09Z | - |
dc.date.issued | 1998 | |
dc.identifier.issn | 00062960 | |
dc.identifier.uri | https://osnascholar.ub.uni-osnabrueck.de/handle/unios/12560 | - |
dc.description.abstract | Photosynthetic water oxidation by photosystem II is mediated by a Mn-4 cluster, a cofactor X still chemically ill-defined, and a tyrosine, Y-Z (D1-Tyr161). Before the final reaction with water proceeds to yield O-2 (transition S-4 --> S-0), two oxidizing equivalents are stored on Mn-4 (S-0 double right arrow S-1 double right arrow S-2), a third on X (S-2 double right arrow S-3), and a forth on Y-Z (S-3 double right arrow S-4). It has been proposed that Y-Z functions as a pure electron transmitter between Mn4X and P-680, or, more recently, that it acts as an abstractor of hydrogen from bound water. We scrutinized the coupling of electron and proton transfer during the oxidation of Y-Z in PSII core particles with intact or impaired oxygen-evolving capacity, The rates of electron transfer to P-680(+), of electrochromism, and of pH transients were determined as a function of the pH, the temperature, and the H/D ratio, In oxygen-evolving material, we found only evidence for electrostatically induced proton release from peripheral amino acid residues but not from Y-Z(ox) itself. The positive charge stayed near Y-Z(ox), and the rate of electron transfer was nearly independent of the pH. In core particles with an impaired Mn-4 cluster, on the other hand, the rate of the electron transfer became strictly dependent on the protonation state of a single base (pK approximate to 7). At pH <7, the rate of electron transfer revealed the same slow rate (t(1/2) approximate to 35 mu s) as that of proton release into the bulk. The deposition of a positive charge around Y-Z(ox) was no longer detected. A large H/D isotope effect (approximate to 2.5) on these rates was also indicative of a steering of electron abstraction by proton transfer. That Y-Z(ox) was deprotonated into the bulk in inactive but not in oxygen-evolving material argues against the proposed role of Y-Z(ox) as an acceptor of hydrogen from water. Instead, the positive charge in its vicinity may shift the equilibrium from bound water to bound peroxide upon S-3 double right arrow S-4 as a prerequisite for the formation of oxygen upon S-4 --> S-0. | |
dc.language.iso | en | |
dc.publisher | AMER CHEMICAL SOC | |
dc.relation.ispartof | BIOCHEMISTRY | |
dc.subject | ABSORBANCE DIFFERENCE SPECTRA | |
dc.subject | Biochemistry & Molecular Biology | |
dc.subject | ELECTRON-TRANSFER | |
dc.subject | EVOLVING SYSTEM | |
dc.subject | MEMBRANE-FRAGMENTS | |
dc.subject | NANOSECOND REDUCTION KINETICS | |
dc.subject | PHOTOSYNTHETIC OXYGEN EVOLUTION | |
dc.subject | PROTON RELEASE | |
dc.subject | RHODOBACTER-SPHAEROIDES | |
dc.subject | SITE-DIRECTED MUTANTS | |
dc.subject | Y-Z | |
dc.title | Function of tyrosine Z in water oxidation by photosystem II: Electrostatical promotor instead of hydrogen abstractor | |
dc.type | review | |
dc.identifier.doi | 10.1021/bi9719152 | |
dc.identifier.isi | ISI:000071824600021 | |
dc.description.volume | 37 | |
dc.description.issue | 4 | |
dc.description.startpage | 1131 | |
dc.description.endpage | 1142 | |
dc.contributor.orcid | 0000-0001-5844-3064 | |
dc.contributor.orcid | 0000-0001-6286-4638 | |
dc.contributor.researcherid | AAH-3608-2021 | |
dc.contributor.researcherid | J-8086-2013 | |
dc.contributor.researcherid | A-7087-2013 | |
dc.contributor.researcherid | R-8391-2016 | |
dc.publisher.place | 1155 16TH ST, NW, WASHINGTON, DC 20036 USA | |
dcterms.isPartOf.abbreviation | Biochemistry | |
crisitem.author.dept | Universität Osnabrück | - |
crisitem.author.dept | FB 05 - Biologie/Chemie | - |
crisitem.author.deptid | fb05 | - |
crisitem.author.orcid | 0000-0001-5844-3064 | - |
crisitem.author.parentorg | Universität Osnabrück | - |
crisitem.author.netid | MuAr001 | - |
crisitem.author.netid | JuWo587 | - |