Taxonomic distribution of proteins containing BCS1_N domains

The tree below includes only several representative species and genera. The complete taxonomic breakdown of all proteins containing BCS1_N domains can be accessed here. Click the counts or percentage values to display the corresponding proteins.

Mitochondrial protein import: recognition of internal import signals ofBCS1 by the TOM complex.

Stan T, Brix J, Schneider-Mergener J, Pfanner N, Neupert W, Rapaport D
Mol Cell Biol. 2003; 23: 2239-50

BCS1, a component of the inner membrane of mitochondria, belongs to thegroup of proteins with internal, noncleavable import signals. Import andintramitochondrial sorting of BCS1 are encoded in the N-terminal 126 aminoacid residues. Three sequence elements were identified in this region,namely, the transmembrane domain (amino acid residues 51 to 68), apresequence type helix (residues 69 to 83), and an import auxiliary region(residues 84 to 126). The transmembrane domain is not required for stablebinding to the TOM complex. The Tom receptors (Tom70, Tom22 and Tom20), asdetermined by peptide scan analysis, interact with the presequence-likehelix, yet the highest binding was to the third sequence element. Wepropose that the initial recognition of BCS1 precursor at the surface ofthe organelle mainly depends on the auxiliary region and does not requirethe transmembrane domain. This essential region represents a novel type ofsignal with targeting and sorting functions. It is recognized by all threeknown mitochondrial import receptors, demonstrating their capacity todecode various targeting signals. We suggest that the BCS1 precursorcrosses the TOM complex as a loop structure and that once the precursoremerges from the TOM complex, all three structural elements are essentialfor the intramitochondrial sorting to the inner membrane.