FtsH proteases in chloroplasts and cyanobacteria

Abstract

FtsH is a membrane‐bound ATP‐dependent metalloprotease complex found in prokaryotes and organelles of eukaryotic cells. It consists of one or two trans‐membrane helices at its amino‐terminus, a highly conserved ATPase domain, which relates it to the AAA protein family, and a zinc‐binding domain towards its carboxy‐terminus that serves as the proteolytic site. Most bacteria contain a single FtsH gene, but the cyanobacterium Synechocystis has four. The Arabidopsis thaliana genome contains 12 genes encoding FtsH proteins, nine of them can be targeted to chloroplasts, whereas the other three are mitochondrial. Chloroplast FtsH protease is located in the thylakoid membrane, where it forms complexes, most likely hexamers, whose ATPase and proteolytic domains are exposed to the stroma. It is involved in the degradation of the D1 protein of photosystem II reaction centre during its repair from photoinhibition, as well as in the degradation of unassembled proteins in the thylakoid and the stroma. In Arabidopsis, FtsH2 is the most abundant isomer, followed by FtsH5, 8 and 1. This hierarchy is well reflected in the severity of the variegated phenotype of mutants in these genes.

The FtsH Protease slr0228 Is Important for Quality Control of Photosystem II in the Thylakoid Membrane of Synechocystis sp. PCC 6803

“…The Arabidopsis thaliana chloroplast also contains a number of FtsH homologues, all nucleus-encoded (16). Of these, FtsH2 (VAR2) has been shown to be involved in D1 degradation (17), but other FtsH members are also likely to participate (18,19).…”

Protein stability and degradation in plastids

“…Taken together, these results suggested that the chloroplast FtsH complex is a hetero-oligomer composed of two types of subunits, each encoded by duplicated genes. Whereas subunits within a type are redundant, the presence of subunits from both types is essential for accumulation of the complex (Adam et al 2005(Adam et al , 2006Zaltsman et al 2005b). Moreover, previous quantification of the different isomers (Sinvany-Villalobo et al 2004) now suggests that the FtsH hexamer is composed of two subunits of 'type A'-FtsH1 and/or FtsH5, and four subunits of 'type B'-FtsH2 and/or FtsH8 (Zaltsman et al 2005b;Adam et al 2006).…”

“…The FtsH gene family in Arabidopsis contains twelve members (for recent reviews, see Adam et al 2005Adam et al , 2006Sakamoto 2006). Products of three of these (FtsH3, FtsH4, and FtsH10) are targeted to the mitochondria whereas the other nine (FtsH1, FtsH2, FtsH5-FtsH9, FtsH11, and FtsH12) are targeted to the chloroplasts, as revealed by transient-expression assays with GFP fusions (Sakamoto et al 2003).…”

“…Immunoblot analysis of isolated organelles suggested that whereas FtsH4 is located exclusively in the mitochondria, FtsH11 is dually targeted to both the mitochondria and chloroplasts (Urantowka et al 2005). The chloroplast-targeted FtsH1 and FtsH5, FtsH2 and FtsH8, and FtsH7 and FtsH9 comprise three pairs of duplicated genes (see phylogenetic trees in Sakamoto et al 2003;Yu et al 2004;Adam et al 2005). Of the four proteins that were indeed identified in chloroplasts, FtsH2 is the most abundant, followed by FtsH5, FtsH8 and FtsH1, in decreasing order of abundance (Sinvany-Villalobo et al 2004).…”

Evolução convergente da protease FtsH5 de Arabidopsis thaliana e seu regulador negativo putativo FIP (FtsH5 interacting protein)

“…A multiplicação dos genes das proteases FtsH se correlaciona fortemente com a evolução da fotossíntese, muito provalmente devido ao aumento do estresse oxidativo e a consequente maior quantidade de danos as proteínas (ADAM et al, 2005). As bactérias contem apenas uma cópia do gene FtsH, ao passo que cianobactérias possuem quatro destes genes (MANN et al, 2000) e as plantas superiores possuem ainda mais cópias, como exemplo A. thaliana possui uma família gênica com 17 membros, com 12 deles codificando para isoformas ativas (GARCIA-LORENZO et al 2006).…”