Splicing before import - an intein in a mitochondrially targeted preprotein folds and is catalytically active in the cytoplasm in vivo.
Nuclear-encoded mitochondrial proteins are cytoplasmically synthesized and imported into the organelle. The intein-containing RecA protein of Mycobacterium tuberculosis, with or without the CoxIVp mitochondrial targeting signal (MTS), was used to determine where a protein targeted to mitochondria folds and becomes catalytically active. Analysis of fractions from Saccharomyces cerevisiae cells expressing RecA without the MTS revealed that RecA and intein proteins remained cytoplasmic. With the MTS, most of RecA was directed to mitochondria, while most of the intein remained in the cytoplasm. The intein therefore folds into a catalytically active state in the cytoplasm prior to RecA import into mitochondria.
Department of Biochemistry and Molecular Biology, University of Louisville School of Medicine, KY 40202, USA.
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LR
Williams
S R
SR
Ellis
A K
AK
Hopper
E O
EO
Davis
N C
NC
Martin
D001483:Base Sequence; D019069:Cell Respiration; D003593:Cytoplasm / Q000378:metabolism; D017931:DNA Primers / Q000235:genetics; D005285:Fermentation; D008928:Mitochondria / Q000378:metabolism; D009169:Mycobacterium tuberculosis / Q000235:genetics / Q000378:metabolism; D017510:Protein Folding; D011498:Protein Precursors / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D011499:Protein Processing, Post-Translational; D012326:RNA Splicing; D011938:Rec A Recombinases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000254:growth & development / Q000378:metabolism
D017931:DNA Primers; D011498:Protein Precursors; D011994:Recombinant Proteins; D011938:Rec A Recombinases