| Type: | Family | Name: | Oxygen-evolving enhancer protein 3 |
| Description: | Oxygenic photosynthesis uses two multi-subunit photosystems (I and II) located in the cell membranes of cyanobacteria and in the thylakoid membranes of chloroplasts in plants and algae. Photosystem II (PSII) has a P680 reaction centre containing chlorophyll 'a' that uses light energy to carry out the oxidation (splitting) of water molecules, and to produce ATP via a proton pump. Photosystem I (PSI) has a P700 reaction centre containing chlorophyll that takes the electron and associated hydrogen donated from PSII to reduce NADP+ to NADPH. Both ATP and NADPH are subsequently used in the light-independent reactions to convert carbon dioxide to glucose using the hydrogen atom extracted from water by PSII, releasing oxygen as a by-product.PSII is a multisubunit protein-pigment complex containing polypeptides both intrinsic and extrinsic to the photosynthetic membrane [, ]. Within the core of the complex, the chlorophyll and beta-carotene pigments are mainly bound to the antenna proteins CP43 (PsbC) and CP47 (PsbB), which pass the excitation energy on to the reaction centre proteins D1 (Qb, PsbA) and D2 (Qa, PsbD) that bind all the redox-active cofactors involved in the energy conversion process. The PSII oxygen-evolving complex (OEC) oxidises water to provide protons for use by PSI, and consists of OEE1 (PsbO), OEE2 (PsbP) and OEE3 (PsbQ). The remaining subunits in PSII are of low molecular weight (less than 10 kDa), and are involved in PSII assembly, stabilisation, dimerisation, and photo-protection []. In PSII, the oxygen-evolving complex (OEC) is responsible for catalysing the splitting of water to O(2) and 4H+. The OEC is composed of a cluster of manganese, calcium and chloride ions bound to extrinsic proteins. In cyanobacteria there are five extrinsic proteins in OEC (PsbO, PsbP-like, PsbQ-like, PsbU and PsbV), while in plants there are only three (PsbO, PsbP and PsbQ), PsbU and PsbV having been lost during the evolution of green plants [].This family represents the PSII OEC protein PsbQ. Both PsbQ and PsbP () are regulators that are necessary for the biogenesis of optically active PSII. The crystal structure of PsbQ from spinach revealed a 4-helical bundle polypeptide. The distribution of positive and negative charges on the protein surface might explain the ability of PsbQ to increase the binding of chloride and calcium ions and make them available to PSII []. | Short Name: | PSII_PsbQ |
| GO Term | Gene Name |
|---|---|
| GO:0005509 | IPR008797 |
| GO:0015979 | IPR008797 |
| GO:0009523 | IPR008797 |
| GO:0009654 | IPR008797 |
| GO:0019898 | IPR008797 |
| GO Term | Gene Name |
|---|---|
| GO:0005509 | IPR008797 |
| GO:0015979 | IPR008797 |
| GO:0009523 | IPR008797 |
| GO:0009654 | IPR008797 |
| GO:0019898 | IPR008797 |
