Functional identification of the SecB homologue in Methanococcus jannaschii and direct interaction of SecB with trigger factor.
In this study Mj0357 protein, a hypothetical protein from Methanococcus jannaschii which shows an 18% sequence identity with SecB from E. coli, has been identified as a functional homologue of SecB in M. jannaschii through a number of biochemical and biophysical examinations. It is composed mostly of beta-strands and exists as a homotetramer in solution. Mj0357 protein exhibits in vitro chaperone-like activity, suppressing thermal aggregation of citrate synthase and binding to partially folded maltose-binding protein. Upon binding to a peptide ligand, the protein undergoes a conformational change to expose a hydrophobic patch on the protein surface. All these physicochemical properties are highly similar to those of E. coli SecB. In addition, E. coli trigger factor (TF) has been shown here for the first time to bind E. coli SecB and Mj0357 protein with low micromolar affinities, indicating that the TF could interact directly along the SecB-dependent translocation pathway. These results indicate that the translocation pathway is conserved and functionally homologous in at least one of the archaeal organisms.
Department of Molecular Cell Biology, Samsung Biomedical Research Institute, Sungkyunkwan University School of Medicine, Suwon 440-746, Republic of Korea.
Sung Chul
SC
Ha
Tae-Hee
TH
Lee
Sun-Shin
SS
Cha
Kyeong Kyu
KK
Kim
D000818:Animals; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D002352:Carrier Proteins / Q000737:chemistry; D002942:Circular Dichroism; D002950:Citrate (si)-Synthase / Q000737:chemistry; D004926:Escherichia coli / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D006358:Hot Temperature; D007700:Kinetics; D058619:Maltose-Binding Proteins; D017017:Methanococcus / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D018832:Molecular Chaperones / Q000737:chemistry / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology; D009206:Myocardium / Q000201:enzymology; D019696:Peptidylprolyl Isomerase / Q000235:genetics / Q000378:metabolism*; D011489:Protein Denaturation; D017510:Protein Folding; D020836:Protein Structure, Quaternary; D017433:Protein Structure, Secondary; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology; D013050:Spectrometry, Fluorescence; D020349:Surface Plasmon Resonance; D013552:Swine; D014462:Ultrafiltration / Q000379:methods
D001426:Bacterial Proteins; D002352:Carrier Proteins; D029968:Escherichia coli Proteins; D058619:Maltose-Binding Proteins; D018832:Molecular Chaperones; D011994:Recombinant Proteins; C057842:SecB protein, Bacteria; D002950:Citrate (si)-Synthase; C403324:trigger factor, E coli; D019696:Peptidylprolyl Isomerase