The Sky Blue Chain The Mold Ftsy And Ffh Structure And Function Of The Initial Study,

Signal recognition particle(SRP) pathway is a highly conserved pathway for protein targeting, and was found sequentially in eukaryotes, prokaryotes and archaebacteria.In prokaryotes, SRP pathway is mainly composed of FtsY, Ffh and scRNA. Homologs of Ffh, scRNA and FtsY were also found in Streptomyces coelicolor by virtue of sequence homologous alignment The SRP pathway in Streptomyces lividans was reported, however, the molecular mechanism and kinetics about streptomycetic SRP pathway are less under investigation.In this work, in S. coelicolor, research about the structure and function, their kinetic properties and their effect factors, and the GTPase activities of FtsY and Ffh is extended. Through bioinformatic tools, physiochemical properties, domain compositions, secondary and tertiary spacial structures, subcellular localization, homologous alignment and phylogenetic trees of FtsY and Ffh proteins are predicted and analyzed. The results show that FtsY and Ffh are comparatively conserved among different genera and both possess NG domains including GTPase activities. However, FtsY in S.coelicolor has a striking transmembrane domain, which cannot be found in FtsY homologs from E.coli and eukaryotic cells. S.coelicolor Ffh is similar to huamn SRP54 protein in the primary structure, and has a long carboxyl terminus as well.And the biochemical experiment indicates that FtsY series(FtsY, FtsY-NG and FtsY-G) and Ffh series(Ffh, Ffh-NG and Ffh-G) in S. coelicolor all have GTPase activities. The GTPase activities between full-length proteins and NG domains almost are fully same, but the GTPase activity of G domain declines significantly. Those demonstrate that N domian including a helix is essential for GTP hydrolysis by FtsY and Ffh, however, the amino terminus in FtsY and the carboxyl terminus in Ffh are on the contrary. Besides, kinetic data show that K_m values in respect of FtsY-G and Ffh-G are highest, whcih explains the point that the differences in GTPase activity is ascribed to those in GTP binding. This is also demonstrated by GTP photoaffinty crosslinking. The effects of temperature, pH and Mg²⁺ onFtsY series and Ffh series are largely similar, but FtsY/FtsY-NG are more stable than FtsY-G, and in Ffh series, Ffh-NG stabilizes more than Ffh-G.Although SRP pathway is highly conserved in life, large differences exist among different genera. In this work, preliminary research about SRP pathway in S.coelicolor is merely made, and the exact molecular mechanism still needs further elucidation.