The mature form of imported mitochondrial proteins undergoes conformational changes upon binding to isolated mitochondria.
Mature mitochondrial proteins (aspartate aminotransferase, malate dehydrogenase, hydroxyacyl coenzyme A dehydrogenase, creatine kinase) and cytosolic proteins (aldolase, glyceraldehyde-3-phosphate dehydrogenase) with a basic pI were found to bind to isolated mitochondria, electrostatic interactions being mainly responsible for their binding. Mitochondrial aspartate aminotransferase bound with a Kd' of 30 nM in 0.6 M sorbitol, 20 mM Hepes/KOH, pH 7.4, at 25 degrees C. Cytosolic aspartate aminotransferase and glutamate dehydrogenase (a protein located in the mitochondrial matrix) both with an acidic pI, did not bind to mitochondria. Treatment of mitochondria with proteinases did not affect the subsequent binding of imported mitochondrial proteins. Their association with both intact and proteinase-treated mitochondria resulted in a marked increase in their susceptibility toward proteinase K. In contrast, the basic cytosolic proteins tested bound only to intact mitochondria and thereby did not become more susceptible toward proteolytic attack. Treatment of mitochondria with adriamycin, a drug binding to acidic phospholipids, prevented the subsequent association of mitochondrial aspartate aminotransferase with mitochondria and the ensuing conformational labilization. Apparently, the mature moiety of imported mitochondrial proteins is partially unfolded upon interaction with the lipid component of the mitochondrial envelope. Both the binding of the mitochondrial proteins and their conformational labilization is independent of ATP and the electrochemical potential across the inner membrane.
Hartmann
C M
CM
Biochemisches Institut der Universität Zürich, Switzerland.
Gehring
H
H
Christen
P
P
D015094:3-Hydroxyacyl CoA Dehydrogenases / Q000737:chemistry / Q000378:metabolism*; D001219:Aspartate Aminotransferases / Q000737:chemistry / Q000378:metabolism*; D003402:Creatine Kinase / Q000737:chemistry / Q000378:metabolism*; D003600:Cytosol / Q000201:enzymology; D004317:Doxorubicin / Q000494:pharmacology; D004591:Electrophoresis, Polyacrylamide Gel; D005634:Fructose-Bisphosphate Aldolase / Q000737:chemistry / Q000378:metabolism; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases / Q000737:chemistry / Q000378:metabolism; D007526:Isoelectric Point; D008291:Malate Dehydrogenase / Q000737:chemistry / Q000378:metabolism*; D008928:Mitochondria / Q000201:enzymology* / Q000378:metabolism; D011485:Protein Binding; D011487:Protein Conformation; D012441:Saccharomyces cerevisiae / Q000648:ultrastructure
D004317:Doxorubicin; D015094:3-Hydroxyacyl CoA Dehydrogenases; D008291:Malate Dehydrogenase; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases; D001219:Aspartate Aminotransferases; D003402:Creatine Kinase; D005634:Fructose-Bisphosphate Aldolase