Psb30 contributes to structurally stabilise the Photosystem II complex in the thermophilic cyanobacterium Thermosynechococcus elongatus

Abstract

A deletion mutant that lacks the Psb30 protein, one of the small subunits of Photosystem II, was constructed in a Thermosynechococcus elongatus strain in which the D1 protein is expressed from the psbA 3 gene (WT*). The ΔPsb30 mutant appears more susceptible to photodamage, has a cytochrome b 559 that is converted into the low potential form, and probably also lacks the PsbY subunit. In the presence of an inhibitor of protein synthesis, the ∆Psb30 lost more rapidly the water oxidation function than the WT* under the high light conditions. These results suggest that Psb30 contributes to structurally and functionally stabilise the Photosystem II complex in preventing the conversion of cytochrome b 559 into the low potential form. Structural reasons for such effects are discussed.