scholarly journals Comparative analysis of the biogenesis of photosystem II in the wild-type and Y-1 mutant of Chlamydomonas reinhardtii.

1988 ◽  
Vol 106 (3) ◽  
pp. 609-616 ◽  
Author(s):  
P Malnoë ◽  
S P Mayfield ◽  
J D Rochaix
Keyword(s):  
Photosystem Ii ◽  
Chlamydomonas Reinhardtii ◽  
Oxygen Evolving Complex ◽  
Wild Type ◽  
Plastid Development ◽  
Photosynthetic System ◽  
In The Wild ◽  
Steady State Levels ◽  
Chloroplast Mrna ◽  
Oxygen Evolving

Expression of the genes of the photosystem II (PSII) core polypeptides D1 and D2, of three proteins of the oxygen evolving complex of PSII and of the light harvesting chlorophyll a/b binding proteins (LHCP) has been compared in wild-type (wt) and in the y-1 mutant of Chlamydomonas reinhardtii. Since wt, but not y-1 cells produce a fully developed photosynthetic system in the dark, comparison of the two has allowed us to distinguish the direct effect of light from the influence of plastid development on gene expression. The PSII core polypeptides and LHCP are nearly undetectable in dark-grown y-1 cells but they accumulate progressively during light induced greening. The levels of these proteins in wt are the same in the light and the dark. The amounts of the proteins of the oxygen evolving complex do not change appreciably in the light or in the dark for both wt and y-1. Steady state levels of chloroplast mRNA encoding the core PSII polypeptides remain nearly constant in the light or the dark and are not affected by the developmental stage of the plastid. Levels of nuclear encoded mRNAs for the oxygen evolving proteins and of LHCP increase during light growth in wt and y-1. In contrast to wt, synthesis of LHCP proteins is not detectable in y-1 cells in the dark but starts immediately after transfer to light, indicating that LHCP synthesis is controlled by a light-induced factor or process. While the rates of synthesis of D1 and D2 are immediately enhanced by light in wt, this increase occurs only after a lag in y-1 and thus must be dependent on an early light-induced event in the plastid. These results show that the biosynthesis of PSII is affected by light directly, by the stage of plastid development, and by the interaction of light and events associated with plastid development.

scholarly journals Complexome profiling on the lpa2 mutant reveals insights into PSII biogenesis and new PSII associated proteins

2021 ◽  
Author(s):  
Benjamin Spaniol ◽  
Julia Lang ◽  
Benedikt Venn ◽  
Lara Schake ◽  
Frederik K Sommer ◽  
...  
Keyword(s):  
Complex Dynamics ◽  
Oxygen Evolving Complex ◽  
Cytochrome B6f Complex ◽  
Wild Type ◽  
Low Light ◽  
Chlorophyll Breakdown ◽  
Associated Proteins ◽  
In The Wild ◽  
Oxygen Evolving ◽  
B6f Complex

We have identified the homolog of LOW PSII ACCUMULATION 2 (LPA2) in Chlamydomonas. A Chlamydomonas lpa2 mutant grew slower in low light and was hypersensitive to high light. PSII maximum quantum efficiency was reduced by 38%. Synthesis and stability of newly made PSII core subunits D1, D2, CP43, and CP47 were not impaired. Complexome profiling revealed that in the mutant CP43 was reduced to ~23%, D1, D2, and CP47 to ~30% of wild-type levels, while small PSII core subunits and components of the oxygen evolving complex were reduced at most by factor two. PSII supercomplexes, dimers, and monomers were reduced to 7%, 26%, and 60% of wild-type levels, while RC47 was increased ~6-fold. Our data indicate that LPA2 acts at a step during PSII assembly without which PSII monomers and especially further assemblies become intrinsically unstable and prone to degradation. Levels of ATP synthase and LHCII were 29% and 27% higher in the mutant than in the wild type, whereas levels of the cytochrome b6f complex were unaltered. While the abundance of PSI core subunits and antennae hardly changed, LHCI antennae were more disconnected in the lpa2 mutant, presumably as an adaptive response to reduce excitation of PSI. The disconnection of LHCA2,9 together with PSAH and PSAG was the prime response, but independent and additional disconnection of LHCA1,3-8 along with PSAK occurred as well. Finally, based on co-migration profiles, we identified three novel putative PSII associated proteins with potential roles in regulating PSII complex dynamics, assembly, and chlorophyll breakdown.

scholarly journals Investigation of substrate water interactions at the high-affinity Mn site in the photosystem II oxygen-evolving complex

2007 ◽  
Vol 363 (1494) ◽  
pp. 1229-1235 ◽  
Author(s):  
Sonita Singh ◽  
Richard J Debus ◽  
Tom Wydrzynski ◽  
Warwick Hillier
Keyword(s):  
Hydrogen Bonding ◽  
Photosystem Ii ◽  
Exchange Rates ◽  
Isotope Exchange ◽  
Water Molecules ◽  
Oxygen Evolving Complex ◽  
Wild Type ◽  
High Affinity ◽  
O Isotope ◽  
Oxygen Evolving

18 O isotope exchange measurements of photosystem II (PSII) in thylakoids from wild-type and mutant Synechocystis have been performed to investigate binding of substrate water to the high-affinity Mn 4 site in the oxygen-evolving complex (OEC). The mutants investigated were D1-D170H, a mutation of a direct ligand to the Mn 4 ion, and D1-D61N, a mutation in the second coordination sphere. The substrate water 18 O exchange rates for D61N were found to be 0.16±0.02 s −1 and 3.03±0.32 s −1 for the slow and fast phases of exchange, respectively, compared with 0.47±0.04 s −1 and 19.7±1.3 s −1 for the wild-type. The D1-D170H rates were found to be 0.70±0.16 s −1 and 24.4±4.6 s −1 and thus are almost within the error limits for the wild-type rates. The results from the D1-D170H mutant indicate that the high-affinity Mn 4 site does not directly bind to the substrate water molecule in slow exchange, but the binding of non-substrate water to this Mn ion cannot be excluded. The results from the D61N mutation show an interaction with both substrate water molecules, which could be an indication that D61 is involved in a hydrogen bonding network with the substrate water. Our results provide limitations as to where the two substrate water molecules bind in the OEC of PSII.

scholarly journals Structural Changes in the Acceptor Site of Photosystem II upon Ca2+/Sr2+ Exchange in the Mn4CaO5 Cluster Site and the Possible Long-Range Interactions

Biomolecules ◽  
2019 ◽  
Vol 9 (8) ◽  
pp. 371
Author(s):  
Koua
Keyword(s):  
Crystal Structure ◽  
Photosystem Ii ◽  
Long Range ◽  
Electron Acceptor ◽  
Structural Changes ◽  
Acceptor Site ◽  
Oxygen Evolving Complex ◽  
Long Range Interactions ◽  
Structural Perturbations ◽  
Oxygen Evolving

The Mn4CaO5 cluster site in the oxygen-evolving complex (OEC) of photosystem II (PSII) undergoes structural perturbations, such as those induced by Ca2+/Sr2+ exchanges or Ca/Mn removal. These changes have been known to induce long-range positive shifts (between +30 and +150 mV) in the redox potential of the primary quinone electron acceptor plastoquinone A (QA), which is located 40 Å from the OEC. To further investigate these effects, we reanalyzed the crystal structure of Sr-PSII resolved at 2.1 Å and compared it with the native Ca-PSII resolved at 1.9 Å. Here, we focus on the acceptor site and report the possible long-range interactions between the donor, Mn4Ca(Sr)O5 cluster, and acceptor sites.

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