Family

Photosystem II Psb28, class 1 (IPR005610)

Short name: PSII_Psb28_class-1

Family relationships

None.

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 [PMID: 12518057, PMID: 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 [PMID: 14871485].

This family represents the low molecular weight transmembrane protein Psb28 (PsbW) found in PSII, where it is a subunit of the oxygen-evolving complex. Psb28 appears to have several roles, including guiding PSII biogenesis and assembly, stabilising dimeric PSII [PMID: 10950961], and facilitating PSII repair after photo-inhibition [PMID: 9335523]. There appears to be two classes of Psb28, class 1 being found predominantly in algae and cyanobacteria, and class 2 being found predominantly in plants. This entry represents class 1 Psb28.

GO terms

Biological Process

GO:0015979 photosynthesis

Molecular Function

No terms assigned in this category.

Cellular Component

GO:0016020 membrane
GO:0009523 photosystem II
GO:0009654 photosystem II oxygen evolving complex

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.
Pfam
TIGRFAMs
ProDom
HAMAP