Mitochondrial protein import: recognition of internal import signals of BCS1 by the TOM complex.
نویسندگان
چکیده
BCS1, a component of the inner membrane of mitochondria, belongs to the group of proteins with internal, noncleavable import signals. Import and intramitochondrial sorting of BCS1 are encoded in the N-terminal 126 amino acid residues. Three sequence elements were identified in this region, namely, the transmembrane domain (amino acid residues 51 to 68), a presequence type helix (residues 69 to 83), and an import auxiliary region (residues 84 to 126). The transmembrane domain is not required for stable binding to the TOM complex. The Tom receptors (Tom70, Tom22 and Tom20), as determined by peptide scan analysis, interact with the presequence-like helix, yet the highest binding was to the third sequence element. We propose that the initial recognition of BCS1 precursor at the surface of the organelle mainly depends on the auxiliary region and does not require the transmembrane domain. This essential region represents a novel type of signal with targeting and sorting functions. It is recognized by all three known mitochondrial import receptors, demonstrating their capacity to decode various targeting signals. We suggest that the BCS1 precursor crosses the TOM complex as a loop structure and that once the precursor emerges from the TOM complex, all three structural elements are essential for the intramitochondrial sorting to the inner membrane.
منابع مشابه
The Translocase of the Outer Membrane of Mitochondria (TOM complex): Recognition of Mitochondrial Targeting Signals
CONTENTS 1. INTRODUCTION 1 1.1. Origin, structure and function of mitochondria 1 1.2. Preprotein import into mitochondria 2 1.3. Mitochondrial targeting signals 6 1.4. The TOM complex 7 1.5. BCS1 protein 10 1.6. Aims of the present study 12
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عنوان ژورنال:
- Molecular and cellular biology
دوره 23 7 شماره
صفحات -
تاریخ انتشار 2003