The mitochondrial receptor complex: a central role of MOM22 in mediating preprotein transfer from receptors to the general insertion pore.
The receptor complex in the mitochondrial outer membrane, which consists of at least seven different proteins, is responsible for the recognition and translocation of cytosolically synthesized preproteins. Two of its subunits, MOM19 and MOM72, function as surface receptors for preproteins. Four other subunits (MOM38, MOM30, MOM8, and MOM7) have been suggested to constitute the general insertion pore (GIP). Here we report on the structure and function of MOM22. MOM22 is anchored in the outer membrane by a single transmembrane segment. The highly negatively charged N-terminal domain is exposed to the cytosol and the C-terminal domain to the intermembrane space. MOM22 appears to be a central component of the receptor complex, required for the transfer of preproteins from the receptors to the GIP. We speculate that the negatively charged domain of MOM22 is involved in the transfer of positively charged signal sequences of preproteins.
Kiebler
M
M
Institut für Physiologische Chemie, Universität München, Federal Republic of Germany.
Keil
P
P
Schneider
H
H
van der Klei
I J
IJ
Pfanner
N
N
Neupert
W
W
D000595:Amino Acid Sequence; D001483:Base Sequence; D003001:Cloning, Molecular; D004271:DNA, Fungal / Q000235:genetics / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics; D005656:Fungal Proteins / Q000096:biosynthesis*; D007150:Immunohistochemistry; D007425:Intracellular Membranes / Q000378:metabolism / Q000648:ultrastructure; D046911:Macromolecular Substances; D008565:Membrane Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D026901:Membrane Transport Proteins; D008854:Microscopy, Electron; D008928:Mitochondria / Q000378:metabolism* / Q000648:ultrastructure; D008969:Molecular Sequence Data; D008970:Molecular Weight; D009492:Neurospora crassa / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D009838:Oligodeoxyribonucleotides; D011487:Protein Conformation; D011498:Protein Precursors / Q000378:metabolism*; D021382:Protein Sorting Signals / Q000378:metabolism; D011956:Receptors, Cell Surface
D004271:DNA, Fungal; D005656:Fungal Proteins; D046911:Macromolecular Substances; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D009838:Oligodeoxyribonucleotides; D011498:Protein Precursors; D021382:Protein Sorting Signals; D011956:Receptors, Cell Surface