| 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 [ ].Photosystem I (PSI) [ ] is an integral membrane protein complex that uses light energy to mediate electron transfer from plastocyanin to ferredoxin. It is found in the chloroplasts of plants and cyanobacteria. PSI is composed of at least 14 different subunits, two of which are small hydrophobic proteins of about 7 to 9 Kd and evolutionary related, PsaG (also known as PSI-G) and PsaK (also known as PSI-K), both integral membrane proteins. Cyanobacteria contain only PsaK []. While cyanobacterial PSI have phycobilisomes to harvest light, eukaryotic PSI have a membrane-imbedded peripheral antenna []. | Name | Photosystem I reaction centre subunit PsaK superfamily |
| Short Name | PSI_centre_PsaK_sf | Type | Homologous_superfamily |
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