Related Experiment Video
Updated: May 25, 2026
06:26
Isolation and Characterization of Intact Phycobilisome in Cyanobacteria
Published on: November 10, 2021
Photosynthetic cytochrome c550
Mercedes Roncel1, Diana Kirilovsky, Fernando Guerrero
1Instituto de Bioquímica Vegetal y Fotosíntesis, Universidad de Sevilla-CSIC, Sevilla, Spain. mroncel@us.es
Biochimica Et Biophysica Acta
|February 1, 2012
Summary
Cytochrome c550 (cyt c550) in photosynthesis stabilizes ions and protects the Mn4Ca cluster. Recent findings suggest a potential redox role for cyt c550 in photosystem II electron transfer.
Area of Science:
- Biochemistry
- Photosynthesis research
- Algal biology
Background:
- Cytochrome c550 (cyt c550) is a membrane protein in photosystem II (PSII) of cyanobacteria and algae.
- It features unusual bis-histidine heme coordination for a c-type cytochrome.
- Cyt c550 stabilizes ions and protects the Mn4Ca cluster in the oxygen-evolving complex.
Purpose of the Study:
- To review existing research on cyt c550.
- To evaluate its function in PSII in light of recent findings.
- To focus on the heme's physical and redox properties.
Main Methods:
- Literature review of cyt c550 studies.
- Analysis of published data on heme coordination and redox potential.
- Integration of recent experimental results.
Main Results:
- The heme's role in cyt c550 has been unclear due to low redox potential in soluble forms.
- Recent studies show more positive redox potentials (+200mV) for cyt c550 bound to PSII.
- This suggests a possible redox function in PSII electron transfer, despite a 22Å distance to the Mn4Ca cluster.
Conclusions:
- New redox potential data opens possibilities for cyt c550's function in PSII electron transfer.
- Further investigation is needed to elucidate the precise role of the heme and electron transfer mechanisms.
- This research contributes to understanding photosynthesis for sustainable applications.
Related Concept Videos
01:43Electron Transport Chain: Complex III and IV
During the electron transport chain, electrons from NADH and FADH2 are first transferred to complexes I and II, respectively. These two complexes then transfer the electrons to ubiquinol, which carries them further to complex III. Complex III passes the electrons across the intermembrane space to Cyt c, which carries them further to complex IV. Complex IV donates electrons to oxygen and reduces it to water. As electrons pass through complexes I, III, and IV, the energy released aids the pumping...
01:22Photosystem II
The multi-protein complex photosystem II (PS II) harvests photons and transfers their energy through its bound pigments to its reaction center, and ultimately to photosystem I (PSI) through the electron transport chain. The pigments responsible for caputirng the light energy in photosystems include chlorophyll a, chlorophyll b, and carotenoids.
The pigment molecules are arranged across two photosystem domains — the antenna complex and the reaction center. The main aim of the pigment molecules...
The pigment molecules are arranged across two photosystem domains — the antenna complex and the reaction center. The main aim of the pigment molecules...
01:27Photosystem I
Although structurally similar to photosystem II (PSII), photosystem I (PSI) is has a different electron supplier and electron acceptor.
Both these photosystems work in concert. An excited electron from PSII is relayed to PSI via an electron transport chain in the thylakoid membrane of the chloroplast, which is comprised of the carrier molecule plastoquinone, the dual-protein cytochrome complex, and plastocyanin. As electrons move between PSII and PSI, they lose energy and must be re-energized...
Both these photosystems work in concert. An excited electron from PSII is relayed to PSI via an electron transport chain in the thylakoid membrane of the chloroplast, which is comprised of the carrier molecule plastoquinone, the dual-protein cytochrome complex, and plastocyanin. As electrons move between PSII and PSI, they lose energy and must be re-energized...
01:29The Photochemical Reaction Center
Reaction centers are pigment-protein complexes that initiate energy conversion from photons to chemical entities. Therefore, photochemical reaction center is a more appropriate term that describes these complexes. The Nobel laureates Robert Emerson and William Arnold provided the first experimental evidence of photochemical reaction centers by demonstrating the participation of nearly 2,500 chlorophyll molecules for the release of just one molecule of oxygen. Despite thousands of photosynthetic...
01:32Photosystems
Photosystems are multiprotein complexes that form the functional units of photosynthesis in plants, algae, and cyanobacteria. They are found embedded in the membrane of tiny sac-like structures called thylakoids placed inside the chloroplast.
Functioning of Photosystems
Photosystems contain many pigment molecules, such as chlorophylls and carotenoids, arranged in a particular organization across two domains — the antenna complex and the reaction center. The main aim of the pigment molecules...
Functioning of Photosystems
Photosystems contain many pigment molecules, such as chlorophylls and carotenoids, arranged in a particular organization across two domains — the antenna complex and the reaction center. The main aim of the pigment molecules...
01:34The Z-Scheme of Electron Transport in Photosynthesis
The light reactions of photosynthesis assume a linear flow of electrons from water to NADP+. During this process, light energy drives the splitting of water molecules to produce oxygen. However, oxidation of water molecules is a thermodynamically unfavorable reaction and requires a strong oxidizing agent. This is accomplished by the first product of light reactions: oxidized P680 (or P680+), the most powerful oxidizing agent known in biology. The oxidized P680 that acquires an electron from the...