An essential novel component of the noncanonical mitochondrial outer membrane protein import system of trypanosomatids.
The mitochondrial outer membrane protein Tom40 is the general entry gate for imported proteins in essentially all eukaryotes. Trypanosomatids lack Tom40, however, and use instead a protein termed the archaic translocase of the outer mitochondrial membrane (ATOM). Here we report the discovery of pATOM36, a novel essential component of the trypanosomal outer membrane protein import system that interacts with ATOM. pATOM36 is not related to known Tom proteins from other organisms and mediates the import of matrix proteins. However, there is a group of precursor proteins whose import is independent of pATOM36. Domain-swapping experiments indicate that the N-terminal presequence-containing domain of the substrate proteins at least in part determines the dependence on pATOM36. Secondary structure profiling suggests that pATOM36 is composed largely of α-helices and its assembly into the outer membrane is independent of the sorting and assembly machinery complex. Taken together, these results show that pATOM36 is a novel component associated with the ATOM complex that promotes the import of a subpopulation of proteins into the mitochondrial matrix.
Department of Chemistry and Biochemistry, University of Bern, CH-3012 Bern, Switzerland.
Mascha
M
Pusnik
Jan
J
Mani
Oliver
O
Schmidt
Moritz
M
Niemann
Silke
S
Oeljeklaus
Felix
F
Schnarwiler
Bettina
B
Warscheid
Trevor
T
Lithgow
Chris
C
Meisinger
André
A
Schneider
D002460:Cell Line; D008928:Mitochondria / Q000378:metabolism; D033681:Mitochondrial Membrane Transport Proteins / Q000737:chemistry / Q000378:metabolism*; D051336:Mitochondrial Membranes / Q000378:metabolism*; D024101:Mitochondrial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D021381:Protein Transport; D015800:Protozoan Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D034622:RNA Interference; D034741:RNA, Small Interfering; D014346:Trypanosoma brucei brucei / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure
D033681:Mitochondrial Membrane Transport Proteins; D024101:Mitochondrial Proteins; D015800:Protozoan Proteins; D034741:RNA, Small Interfering