title: A putative metal-binding site in the beta subunit of rat mitochondrial processing peptidase is essential for its catalytic activity.
abstract: Mitochondrial processing peptidase (MPP) consists of alpha- and beta-subunits (alpha-MPP and beta-MPP). beta-MPP has a putative metal-binding sequence (HXXEH). To determine whether the sequence of beta-MPP is essential for the enzymatic activity, we individually mutated the histidines and glutamic acid to arginines and glutamine, respectively. The wild-type and mutated beta-MPPs were co-expressed with alpha-MPP in Escherichia coli. All three mutants had completely lost the activity, whereas the lost activity was recovered on the addition of wild-type beta-MPP. The activity of the wild-type enzyme was reduced by the mutant beta-MPPs. We conclude from these observations that the HXXEH region is involved in the formation of the active site and that beta-MPP is the catalytic subunit of MPP.
mesh_terms: D000325:Adrenodoxin / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D008666:Metalloendopeptidases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008930:Mitochondria, Liver / Q000201:enzymology*; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D017354:Point Mutation; D011499:Protein Processing, Post-Translational; D051381:Rats; D011994:Recombinant Proteins / Q000378:metabolism; D000096122:Mitochondrial Processing Peptidase
chemical_list: D000325:Adrenodoxin; D008666:Metalloendopeptidases; D011994:Recombinant Proteins; D000096122:Mitochondrial Processing Peptidase