FtsH2 and FtsH5: two homologous subunits use different integration mechanisms leading to the same thylakoid multimeric complex

Autor(es)

Rodrigues, Ricardo A. O. ^[1] ; Silva-Filho, Marcio C. ^[1] ; Cline, Kenneth ^[2]

Afiliação do(s) autor(es)

^[1] Univ Sao Paulo, Dept Genet, Escola Super Agr Luiz de Queiroz, Piracicaba, SP - Brazil

^[2] Univ Florida, Dept Hort Sci, Gainesville, FL - USA

• Tipo de documento: Artigo Científico
• Fonte: Plant Journal; v. 65, n. 4, p. 600-609, FEB 2011.
• Citações Web of Science: 21

Resumo

P>The Arabidopsis thylakoid FtsH protease complex is composed of FtsH1/FtsH5 (type A) and FtsH2/FtsH8 (type B) subunits. Type A and type B subunits display a high degree of sequence identity throughout their mature domains, but no similarity in their amino-terminal targeting peptide regions. In chloroplast import assays, FtsH2 and FtsH5 were imported and subsequently integrated into thylakoids by a two-step processing mechanism that resulted in an amino-proximal lumenal domain, a single transmembrane anchor, and a carboxyl proximal stromal domain. FtsH2 integration into washed thylakoids was entirely dependent on the proton gradient, whereas FtsH5 integration was dependent on NTPs, suggesting their integration by Tat and Sec pathways, respectively. This finding was corroborated by in organello competition and by antibody inhibition experiments. A series of constructs were made in order to understand the molecular basis for different integration pathways. The amino proximal domains through the transmembrane anchors were sufficient for proper integration as demonstrated with carboxyl-truncated versions of FtsH2 and FtsH5. The mature FtsH2 protein was found to be incompatible with the Sec machinery as determined with targeting peptide-swapping experiments. Incompatibility does not appear to be determined by any specific element in the FtsH2 domain as no single domain was incompatible with Sec transport. This suggests an incompatible structure that requires the intact FtsH2. That the highly homologous type A and type B subunits of the same multimeric complex use different integration pathways is a striking example of the notion that membrane insertion pathways have evolved to accommodate structural features of their respective substrates. (AU)

• Processo FAPESP: 07/57806-6 - Decifrando os mecanismos moleculares envolvidos na localização de membros da família das FtsHs plastidiais nas membranas dos tilacóides
• Beneficiário: Ricardo Augusto de Oliveira Rodrigues
• Modalidade de apoio: Bolsas no Brasil - Doutorado
• Processo FAPESP: 08/52067-3 - Herbivoria e o transporte intracelular de proteínas
• Beneficiário: Márcio de Castro Silva Filho
• Modalidade de apoio: Auxílio à Pesquisa - Programa BIOEN - Temático