Efficient but aberrant cleavage of mitochondrial precursor proteins by the chloroplast stromal processing peptidase.
Cytosol-synthesized chloroplast and mitochondrial precursor proteins are proteolytically processed after import by highly specific, metal-dependent soluble enzymes: the stromal processing peptidase (SPP) and the matrix processing peptidase (MPP), respectively. We have used in vitro processing assays to compare the reaction specificities of highly purified preparations of pea SPP and Neurospora crassa MPP, both of which are unable to cleave a variety of 'foreign' proteins. We show that SPP can cleave all five mitochondrial precursor proteins tested, namely cyclophilin, the beta subunit of the F1-ATPase complex, the Rieske FeS protein, the alpha-MPP subunit and cytochrome b2. In contrast, MPP is unable to cleave any chloroplast precursor proteins tested. Several of the mitochondrial precursor proteins are cleaved more efficiently by SPP than are many authentic chloroplast precursor proteins but, in each case, cleavage takes place at a site or sites which are N-terminal to the authentic MPP site; pre-cyclophilin is cleaved 5 residues upstream of the MPP site and the precursor of the beta subunit of the F1-ATPase complex is cleaved at sites 5 and 12 residues upstream. We discuss the implications of these data for the SPP reaction mechanism.
Bassham
D C
DC
Department of Biological Sciences, University of Warwick, England.
Creighton
A M
AM
Arretz
M
M
Brunner
M
M
Robinson
C
C
D000591:Amino Acid Isomerases / Q000378:metabolism; D000595:Amino Acid Sequence; D001665:Binding Sites; D002352:Carrier Proteins / Q000378:metabolism; D002736:Chloroplasts / Q000201:enzymology*; D014450:Electron Transport Complex III; D007887:Fabaceae / Q000201:enzymology; D007506:Iron-Sulfur Proteins / Q000378:metabolism; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D042844:L-Lactate Dehydrogenase (Cytochrome); D008666:Metalloendopeptidases / Q000378:metabolism*; D008928:Mitochondria / Q000737:chemistry*; D008969:Molecular Sequence Data; D009492:Neurospora crassa / Q000201:enzymology; D019696:Peptidylprolyl Isomerase; D010940:Plant Proteins; D010946:Plants, Medicinal; D011498:Protein Precursors / Q000378:metabolism*; D006180:Proton-Translocating ATPases / Q000378:metabolism; D013379:Substrate Specificity; D000096122:Mitochondrial Processing Peptidase
D000591:Amino Acid Isomerases; D002352:Carrier Proteins; D014450:Electron Transport Complex III; D007506:Iron-Sulfur Proteins; D007770:L-Lactate Dehydrogenase; D042844:L-Lactate Dehydrogenase (Cytochrome); D008666:Metalloendopeptidases; D019696:Peptidylprolyl Isomerase; D010940:Plant Proteins; D011498:Protein Precursors; D006180:Proton-Translocating ATPases; D000096122:Mitochondrial Processing Peptidase; C037989:Rieske iron-sulfur protein; C071986:stromal processing peptidase