Summary: Photosystem II 12 kDa extrinsic protein (PsbU)
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Photosystem II 12 kDa extrinsic protein (PsbU) Provide feedback
This family consists of several photosystem II 12 kDa extrinsic protein (PsbU) proteins from cyanobacteria and algae. PsbU is an extrinsic protein of the photosystem II complex of cyanobacteria and red algae. PsbU is known to stabilise the oxygen-evolving machinery of the photosystem II complex against heat-induced inactivation . This family appears to be related to the Helix-hairpin-helix domain.
Nishiyama Y, Los DA, Murata N; , Plant Physiol 1999;120:301-308.: PsbU, a protein associated with photosystem II, is required for the acquisition of cellular thermotolerance in synechococcus species PCC 7002 PUBMED:10318707 EPMC:10318707
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This tab holds annotation information from the InterPro database.
InterPro entry IPR010527
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 [PUBMED:12518057, PUBMED:15100025]. 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 [PUBMED:14871485].
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 [PUBMED:15258264].
This family represents the PSII extrinsic protein PsbU, which forms part of the OEC in cyanobacteria and red algae. PsbU acts to stabilise the oxygen-evolving machinery of PSII against heat-induced inactivation, which is crucial for cellular thermo-tolerance [PUBMED:10318707].
The mapping between Pfam and Gene Ontology is provided by InterPro. If you use this data please cite InterPro.
|Cellular component||photosystem II (GO:0009523)|
|extrinsic to membrane (GO:0019898)|
|oxygen evolving complex (GO:0009654)|
|Biological process||photosystem II stabilization (GO:0042549)|
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This superfamily includes Helix-hairpin-helix DNA-binding domains.
The clan contains the following 20 members:Cdd1 DNA_pol_lambd_f DUF3173 DUF4332 DUF655 HHH HhH-GPD HHH_2 HHH_3 HHH_4 HHH_5 HHH_6 HHH_7 HHH_8 IMS_HHH PsbU RNA_pol_A_CTD T2SK TfoX_C Transposase_20
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Curation and family details
|Seed source:||Pfam-B_13782 (release 10.0)|
|Author:||Moxon SJ, Bateman A|
|Number in seed:||24|
|Number in full:||89|
|Average length of the domain:||91.40 aa|
|Average identity of full alignment:||44 %|
|Average coverage of the sequence by the domain:||59.54 %|
|HMM build commands:||
build method: hmmbuild -o /dev/null HMM SEED
search method: hmmsearch -Z 23193494 -E 1000 --cpu 4 HMM pfamseq
|Family (HMM) version:||6|
|Download:||download the raw HMM for this family|
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For those sequences which have a structure in the Protein DataBank, we use the mapping between UniProt, PDB and Pfam coordinate systems from the PDBe group, to allow us to map Pfam domains onto UniProt sequences and three-dimensional protein structures. The table below shows the structures on which the PsbU domain has been found. There are 17 instances of this domain found in the PDB. Note that there may be multiple copies of the domain in a single PDB structure, since many structures contain multiple copies of the same protein seqence.
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