PMID:8940120
| Citation |
Akiyama, Y, Kihara, A, Tokuda, H and Ito, K (1996) FtsH (HflB) is an ATP-dependent protease selectively acting on SecY and some other membrane proteins. J. Biol. Chem. 271:31196-201 |
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| Abstract |
The FtsH protein is a membrane-bound ATPase of Escherichia coli that was proposed to be involved in membrane protein assembly as well as degradation of some unstable proteins. SecY, a subunit of protein translocase, is FtsH dependently degraded in vivo when it fails to associate with its partner (the SecE protein). We constructed a series of mutants in which mutations were introduced into conserved residues in the two ATP binding consensus sequences or the zinc binding sequence of FtsH. We purified wild-type and mutant FtsH proteins by making use of a polyhistidine tag attached to their carboxyl termini. Complementation analysis and ATPase activity assays in vitro indicated that, of the two sets of ATP binding sequence motifs, the one located C-terminally (A1) is essential for ATPase activity and in vivo functioning of FtsH. Wild-type FtsH protein degraded purified SecY in an ATP hydrolysis-dependent manner in vitro. Mutant proteins without ATPase activity were inactive in proteolysis. A zinc binding motif mutant showed a decreased proteolytic activity. SecY and FtsH were cross-linkable with each other in the membrane, provided that FtsH had an ATPase-inactivating mutation. These results demonstrate that FtsH binds to and degrades SecY, its A1 motif and the zinc binding motif being important for the proteolytic activity. FtsH-dependent proteolysis was also demonstrated for SecY in crude membrane extracts, whereas a majority of other membrane proteins were not degraded, indicating that FtsH has high selectivity in protein degradation. |
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| Keywords |
ATP-Dependent Proteases; Adenosine Triphosphatases/metabolism; Adenosine Triphosphate/metabolism; Amino Acid Sequence; Bacterial Proteins/metabolism; Binding Sites; Electrophoresis, Polyacrylamide Gel; Endopeptidases/metabolism; Escherichia coli Proteins; Membrane Proteins/metabolism; Molecular Sequence Data; Mutagenesis, Site-Directed; Phenotype; Plasmids/metabolism |
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