Nbv. Sepuri et al., GTP HYDROLYSIS IS ESSENTIAL FOR PROTEIN IMPORT INTO THE MITOCHONDRIALMATRIX, The Journal of biological chemistry, 273(3), 1998, pp. 1420-1424
Protein import into the innermost compartment of mitochondria (the mat
rix) requires a membrane potential (Delta Psi) across the inner membra
ne, as well as ATP-dependent interactions with chaperones in the matri
x and cytosol, The role of nucleoside triphosphates other than ATP dur
ing import into the matrix, however, remains to be determined, Import
of urea-denatured precursors does not require cytosolic chaperones, We
have there fore used a purified and urea-denatured preprotein in our
import assays to bypass the requirement of external ATP, Using this mo
dified system, we demonstrate that GTP stimulates protein import into
the matrix; the stimulatory effect is directly mediated by GTP hydroly
sis and does not result from conversion of GTP to ATP, Both external G
TP and matrix ATP are necessary; neither one can substitute for the ot
her if efficient import is to be achieved, These results suggest a ''p
ush-pull'' mechanism of import, which may be common to other posttrans
lational translocation pathways.