FtsH recognizes proteins with unfolded structure and hydrolyzes the carboxyl side of hydrophobic residues.
FtsH of Escherichia coli is an essential membrane-integrated ATP-dependent protease. We cloned a gene for an FtsH homolog (T. FtsH) from Thermus thermophilus HB8, expressed it in E. coli, and purified the expressed protein. ATPase activity of T.FtsH was activated by proteins with unfolded structure ( alpha-casein and pepsin), and T.FtsH digested these proteins in an ATP-, Zn(2+)-dependent manner. alpha-Lactalbumin was digested by T.FtsH when it was largely unfolded, but not in its native form. Analysis of the proteolytic products revealed that, in most cases, T.FtsH cleaved the C-terminal side of hydrophobic residues and produced a characteristic set of small peptides (<30 kDa) without releasing a large intermediate. Thus, T.FtsH recognizes the unfolded structure of the proteins and progressively digests them at the expense of ATP. A soluble domain of T.FtsH, which lacked the N-terminal two transmembrane helices, was also prepared but was found to retain neither ATPase nor protease activities. Thus, the membrane segment appeared to be indispensable for these activities of T.FtsH.
Asahara
Y
Y
Research Laboratory of Resources Utilization, Tokyo Institute of Technology, Nagatsuta Yokohama 226-8503, Japan.
Atsuta
K
K
Motohashi
K
K
Taguchi
H
H
Yohda
M
M
Yoshida
M
M
D049069:ATP-Dependent Proteases; D000251:Adenosine Triphosphatases / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D002364:Caseins / Q000378:metabolism; D003001:Cloning, Molecular; D029968:Escherichia coli Proteins; D005798:Genes, Bacterial; D007768:Lactalbumin / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D008666:Metalloendopeptidases / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D010434:Pepsin A / Q000378:metabolism; D011489:Protein Denaturation; D017510:Protein Folding; D011994:Recombinant Proteins / Q000378:metabolism; D013379:Substrate Specificity; D016963:Thermus thermophilus / Q000201:enzymology* / Q000235:genetics; D015032:Zinc
D001426:Bacterial Proteins; D002364:Caseins; D029968:Escherichia coli Proteins; D008565:Membrane Proteins; D011994:Recombinant Proteins; D007768:Lactalbumin; D049069:ATP-Dependent Proteases; C513383:FtsH protein, E coli; D010434:Pepsin A; D008666:Metalloendopeptidases; D000251:Adenosine Triphosphatases; D015032:Zinc