Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
1927135 | Archives of Biochemistry and Biophysics | 2007 | 9 Pages |
Abstract
We reported previously that the human factor B precursor is a 215-amino acid polypeptide, the first 40 amino acid residues of which function as a mitochondrial targeting presequence [G.I. Belogrudov, Y. Hatefi, J. Biol. Chem. 277 (2002) 6097-6103]. Confocal microscopy of live HEK293 cells, transiently transfected with factor B constructs tagged at the C-terminus with green fluorescent protein (GFP) revealed that either a 40- or 25-residue presequence localized factor B to mitochondria. Indirect immunofluorescent labeling of fixed, permeabilized HEK293 cells that were transiently transfected with a construct lacking a presequence, showed diffuse, intracellular staining that was consistent with targeting of ectopically expressed factor B to cellular compartments distinct from the mitochondria. Mutants in which either Metâ25 or both Metâ25/Metâ24 residues of the presequence were deleted exhibited decreased or undetectable levels, respectively, of the GFP-tagged factor B. The factor B presequence alone was shown to target a reporter polypeptide GFP to mitochondria. Our studies, therefore, demonstrate that a 24-residue presequence is sufficient to localize factor B to mitochondria, and suggest that the human factor B precursor is a 199-amino acid polypeptide.
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Authors
Grigory I. Belogrudov,