TY  - JOUR
A1  - Boudreaux, Brent
A1  - MacMillan, Fraser
A1  - Teutloff, Christian Bork
A1  - Agalarov, Rufat
A1  - Gu, Feifei
A1  - Grimaldi, Stéphane
A1  - Bittl, Robert
A1  - Brettel, Klaus
A1  - Redding, Kevin
T1  - Mutations in both sides of the photosystem I reaction center identify the phylloquinone observed by electron paramagnetic resonance spectroscopy
T2  - Journal of biological chemistry
N2  - The core of photosystem I (PS1) is composed of the two related integral membrane polypeptides, PsaA and PsaB, which bind two symmetrical branches of cofactors, each consisting of two chlorophylls and a phylloquinone, that potentially link the primary electron donor and the tertiary acceptor. In an effort to identify amino acid residues near the phylloquinone binding sites, all tryptophans and histidines that are conserved between PsaA and PsaB in the region of the 10th and 11th transmembrane alpha-helices were mutated in Chlamydomonas reinhardtii. The mutant PS1 reaction centers appear to assemble normally and possess photochemical activity. An electron paramagnetic resonance (EPR) signal attributed to the phylloquinone anion radical (A(1)(-)) can be observed either transiently or after illumination of reaction centers with pre-reduced iron-sulfur clusters. Mutation of PsaA-Trp(693) to Phe resulted in an inability to photo-accumulate A(1)(-), whereas mutation of the analogous tryptophan in PsaB (PsaB-Trp(673)) did not produce this effect. The PsaA-W693F mutation also produced spectral changes in the time-resolved EPR spectrum of the P(700)(+) A(1)(-) radical pair, whereas the analogous mutation in PsaB had no observable effect. These observations indicate that the A(1)(-) phylloquinone radical observed by EPR occupies the phylloquinone-binding site containing PsaA-Trp(693). However, mutation of either tryptophan accelerated charge recombination from the terminal Fe-S clusters.
Y1  - 2021
UR  - http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/75994
UR  - https://nbn-resolving.org/urn:nbn:de:hebis:30:3-759941
SN  - 0021-9258
VL  - 276.2001
IS  - 40
SP  - 37299
EP  - 37306
PB  - American Society for Biochemistry and Molecular Biology Publications
CY  - Bethesda, Md
ER  -