TY - JOUR
T1 - Carotenoid dark state to chlorophyll energy transfer in isolated light-harvesting complexes CP24 and CP29
AU - Gacek, Daniel A.
AU - Holleboom, Christoph-Peter
AU - Liao, Pen-Nan
AU - Negretti, Marco
AU - Croce, Roberta
AU - Walla, Peter Jomo
PY - 2020/1
Y1 - 2020/1
N2 - We present a comparison of the energy transfer between carotenoid dark states and chlorophylls for the minor complexes CP24 and CP29. To elucidate the potential involvement of certain carotenoid–chlorophyll coupling sites in fluorescence quenching of distinct complexes, varying carotenoid compositions and mutants lacking chlorophylls at specific binding sites were examined. Energy transfers between carotenoid dark states and chlorophylls were compared using the coupling parameter, ΦCouplingCar S1-Chl, which is calculated from the chlorophyll fluorescence observed after preferential carotenoid two-photon excitation. In CP24, artificial reconstitution with zeaxanthin leads to a significant reduction in the chlorophyll fluorescence quantum yield, Φ
F1, and a considerable increase in ΦCouplingCar S1-Chl. Similar effects of zeaxanthin were also observed in certain samples of CP29. In CP29, also the replacement of violaxanthin by the sole presence of lutein results in a significant quenching and increased ΦCouplingCar S1-Chl. In contrast, the replacement of violaxanthin by lutein in CP24 is not significantly increasing ΦCouplingCar S1-Chl. In general, these findings provide evidence that modification of the electronic coupling between carotenoid dark states and chlorophylls by changing carotenoids at distinct sites can significantly influence the quenching of these minor proteins, particularly when zeaxanthin or lutein is used. The absence of Chl612 in CP24 and of Chl612 or Chl603 in CP29 has a considerably smaller effect on Φ
F 1 and ΦCouplingCar S1-Chl than the influence of some carotenoids reported above. However, in CP29 our results indicate slightly dequenching and decreased ΦCouplingCar S1-Chl when these chlorophylls are absent. This might indicate that both, Chl612 and Chl603 are involved in carotenoid-dependent quenching in isolated CP29.
AB - We present a comparison of the energy transfer between carotenoid dark states and chlorophylls for the minor complexes CP24 and CP29. To elucidate the potential involvement of certain carotenoid–chlorophyll coupling sites in fluorescence quenching of distinct complexes, varying carotenoid compositions and mutants lacking chlorophylls at specific binding sites were examined. Energy transfers between carotenoid dark states and chlorophylls were compared using the coupling parameter, ΦCouplingCar S1-Chl, which is calculated from the chlorophyll fluorescence observed after preferential carotenoid two-photon excitation. In CP24, artificial reconstitution with zeaxanthin leads to a significant reduction in the chlorophyll fluorescence quantum yield, Φ
F1, and a considerable increase in ΦCouplingCar S1-Chl. Similar effects of zeaxanthin were also observed in certain samples of CP29. In CP29, also the replacement of violaxanthin by the sole presence of lutein results in a significant quenching and increased ΦCouplingCar S1-Chl. In contrast, the replacement of violaxanthin by lutein in CP24 is not significantly increasing ΦCouplingCar S1-Chl. In general, these findings provide evidence that modification of the electronic coupling between carotenoid dark states and chlorophylls by changing carotenoids at distinct sites can significantly influence the quenching of these minor proteins, particularly when zeaxanthin or lutein is used. The absence of Chl612 in CP24 and of Chl612 or Chl603 in CP29 has a considerably smaller effect on Φ
F 1 and ΦCouplingCar S1-Chl than the influence of some carotenoids reported above. However, in CP29 our results indicate slightly dequenching and decreased ΦCouplingCar S1-Chl when these chlorophylls are absent. This might indicate that both, Chl612 and Chl603 are involved in carotenoid-dependent quenching in isolated CP29.
KW - CP24
KW - CP29
KW - Carotenoids
KW - Chlorophylls
KW - Electronic coupling
KW - Photosynthetic regulation
UR - http://www.scopus.com/inward/record.url?scp=85074716275&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85074716275&partnerID=8YFLogxK
U2 - 10.1007/s11120-019-00676-z
DO - 10.1007/s11120-019-00676-z
M3 - Article
SN - 0166-8595
VL - 143
SP - 19
EP - 30
JO - Photosynthesis Research
JF - Photosynthesis Research
IS - 1
ER -