PsbH | Small subunit H of PSII

The PsbH protein was originally named 10- or 9-kDa phosphoprotein in higher plant chloroplasts. It is encoded by the plastome in algae and higher plants. PsbH is also present in cyanobacteria, where it exhibits 56% amino acid identity with the corresponding protein from Arabidopsis. The protein contains 63–90 amino acids, depending on the species, with molecular masses between 7.0 and 9.9 kDa.PsbH is an intrinsic membrane protein with a single transmembrane helix and its N-terminal region has been suggested to be exposed to the stromal side of the thylakoid membrane. Presence of PsbH already present in etiolated tissue can indicate that the protein may be involved in early stages of PSII assembly.Obtained biochemical data from PSII complexes isolated from spinach suggest that PsbH, together with other PSII phosphoproteins, may be required for D1 protein turnover by regulating dimeric and monomeric PSII transition through their phosphorylation and dephosphorylation.