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

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