Auxiliary functions in photosynthesis: the role of the FtsH protease

Abstract

Oxygenic photosynthesis can be described effectively by using two long-standing models: the Z-scheme and the chemiosmotic hypothesis. However, these models do not reveal the dynamic nature of the thylakoid membrane and the four major complexes that it binds. The composition of the photosynthetic apparatus is continually changing in response to a range of environmental stimuli. In addition, many photosynthetic components have some of the highest turnover rates in Nature. Changes in composition and turnover of photosynthetic components require the degradation of existing and damaged polypeptides and the resynthesis and co-ordinated assembly of new polypeptides and their associated cofactors. This is achieved by several auxiliary functions, including proteolysis, protein targeting and the action of molecular chaperones. Some of the components involved in these functions, such as translocons, chaperones and proteases, have been identified but many of the auxiliary functions of photosynthesis remain uncharacterized. Among the proteases known to be associated with the thylakoids is the zinc metalloprotease FtsH, which might also act as a chaperone. Here we provide an overview of the thylakoid FtsH protease and discuss its role in the maintenance and assembly of the photosynthetic apparatus.

Early emergence of the FtsH proteases involved in photosystem II repair

“…Why the FtsH4 homocomplex does not seem to play a major role in PSII repair even though it is found in the thylakoid membrane is unclear. One possible reason might be that specific interactions are required for binding of SynFtsH2/3 to damaged PSII, possibly involving the transmembrane regions of FtsH plus sequences interconnecting the two transmembrane regions on the lumenal side of the membrane (Bailey et al 2001). In addition, substrate recognition might also be mediated via adaptor proteins (Kirstein et al 2009).…”

Involvement of the HtrA family of proteases in the protection of the cyanobacterium Synechocystis PCC 6803 from light stress and in the repair of photosystem II

“…(e) Levels of FtsH in the htrA triple mutant Previous work has implicated a role for FtsH (slr0228) in the early steps of D1 degradation (Bailey et al 2001). To assess whether inactivation of the HtrA family of proteases had affected the expression of the various FtsH proteases, immunoblotting was performed on the samples obtained from the D mutant and WT during exposure to high light, either in the presence or absence of protein synthesis.…”

“…We have chosen the FtsH and HtrA (the latter is also known as DegP) families of proteases for study because of their conserved role in nature in the degradation of damaged or unassembled proteins (reviewed by Pallen & Wren 1997) and also because these types of protease are found in the chloroplast (Lindahl et al 1996;Itzhaki et al 1998) and, more recently, have been linked to D1 degradation from studies in vitro (Lindahl et al 2000;Haußü hl et al 2001). Of the FtsH family of proteases in Synechocystis 6803, we have so far identi ed one member (Cyanobase designation slr0228) that is important for optimizing the D1 repair cycle, probably at an early step in D1 degradation (Bailey et al 2001 Arrows within the resistance cassettes indicate the direction of transcription of the enzymes conferring antibiotic-resistance. (b) Con rmation of the disruption of the htrA, hhoA and hhoB genes in D by PCR using the forward (F) and reverse (R) gene-speci c primers indicated in (a).…”

From Single Genes to Co-Expression Networks: Extracting Knowledge from Barley Functional Genomics

“…The group of heterogeneous genes, belonging to 'Others' in Figure 2 but still photosynthesisrelated or at least chloroplast-related includes for example genes coding for a Ftsh protease-like protein (Bailey et al, 2001), for a cyclophilin type protein (Romano et al, 2004), for an oxygen evolving system-related protein, for a clp protease (Shikanai et al, 2001).…”