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Bacterial signal peptide that functions as a mitochondrial import leader
Author(s) -
Mukhopadhyay Abhijit,
Weiner Henry
Publication year - 2006
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.20.4.a517-c
Subject(s) - periplasmic space , peptide , signal peptide , biochemistry , hela , mitochondrion , biology , peptide sequence , microbiology and biotechnology , cell , escherichia coli , gene
A phage display technique employed to find binding partners of Tom 20, a member of the mitochondrial import apparatus, identified two 12‐mer peptides. One had some identity with a mitochondrial inner membrane protein; the other had high homology (seven identical and three similar) to an E. coli periplasmic signal peptide (Toho‐1). The Toho‐1 leader was capable of carrying proteins into mitochondria in both isolated and transformed HeLa cells. This finding shows that a bacteria leader can function in mitochondrial import. In an attempt to correlate import capability and Tom 20 binding, a bacteria two hybrid system was employed using mutated versions of the leader from both aldehyde dehydrogenase (ALDH) and ornithine transcarbamoylase (OTC). Previous NMR studies showed that leucine residues in the leader were in contact with Tom 20. This observation was verified. However, the mutated ALDH peptide (L15, 18 A) that did not bind well to Tom 20 still was imported to HeLa cell mitochondria. In contrast, the mutated OTC leader (L5,8,9A) that did not bind to Tom 20 was imported less well in transformed HeLa cells than was native OTC. First, these observations show that the binding domain can be anywhere in the leader since it was in the C‐termini of ALDH and the N‐termini of OTC. Second, it shows that binding to Tom 20 might not be a good predictor of whether or not a peptide can function in import. The peptide that bound to Tom 20, which was similar to the N‐terminal leader of Toho‐1, had the sequence H SLK N SMLTVMA (underline show identical and italic show similar amino acids) could not import a protein even though it bound Tom 20. This work was supported in part by NIH Grants AA10795 and GM 53269.