scholarly journals An essential novel component of the noncanonical mitochondrial outer membrane protein import system of trypanosomatids

2012 ◽  
Vol 23 (17) ◽  
pp. 3420-3428 ◽  
Author(s):  
Mascha Pusnik ◽  
Jan Mani ◽  
Oliver Schmidt ◽  
Moritz Niemann ◽  
Silke Oeljeklaus ◽  
...  
Keyword(s):  
Membrane Protein ◽  
Outer Membrane ◽  
Outer Membrane Protein ◽  
Protein Import ◽  
Matrix Proteins ◽  
Mitochondrial Outer Membrane ◽  
Outer Mitochondrial Membrane ◽  
Precursor Proteins ◽  
Substrate Proteins ◽  
Import System

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.

scholarly journals Outer membrane protein functions as integrator of protein import and DNA inheritance in mitochondria

2016 ◽  
Vol 113 (31) ◽  
pp. E4467-E4475 ◽  
Author(s):  
Sandro Käser ◽  
Silke Oeljeklaus ◽  
Jiří Týč ◽  
Sue Vaughan ◽  
Bettina Warscheid ◽  
...  
Keyword(s):  
Membrane Protein ◽  
Outer Membrane ◽  
Outer Membrane Protein ◽  
Protein Import ◽  
Mitochondrial Protein ◽  
In Vitro Assays ◽  
Mitochondrial Outer Membrane ◽  
Mitochondrial Genomes ◽  
Dual Function ◽  
Complex Assembly

Trypanosomatids are one of the earliest diverging eukaryotes that have fully functional mitochondria. pATOM36 is a trypanosomatid-specific essential mitochondrial outer membrane protein that has been implicated in protein import. Changes in the mitochondrial proteome induced by ablation of pATOM36 and in vitro assays show that pATOM36 is required for the assembly of the archaic translocase of the outer membrane (ATOM), the functional analog of the TOM complex in other organisms. Reciprocal pull-down experiments and immunofluorescence analyses demonstrate that a fraction of pATOM36 interacts and colocalizes with TAC65, a previously uncharacterized essential component of the tripartite attachment complex (TAC). The TAC links the single-unit mitochondrial genome to the basal body of the flagellum and mediates the segregation of the replicated mitochondrial genomes. RNAi experiments show that pATOM36, in line with its dual localization, is not only essential for ATOM complex assembly but also for segregation of the replicated mitochondrial genomes. However, the two functions are distinct, as a truncated version of pATOM36 lacking the 75 C-terminal amino acids can rescue kinetoplast DNA missegregation but not the lack of ATOM complex assembly. Thus, pATOM36 has a dual function and integrates mitochondrial protein import with mitochondrial DNA inheritance.

A yeast mitochondrial outer membrane protein essential for protein import and cell viability

Nature ◽  
1990 ◽  
Vol 348 (6302) ◽  
pp. 605-609 ◽  
Author(s):  
Kevin P. Baker ◽  
Angela Schaniel ◽  
Dietmar Vestweber ◽  
Gottfried Schatz
Keyword(s):  
Membrane Protein ◽  
Cell Viability ◽  
Outer Membrane ◽  
Outer Membrane Protein ◽  
Protein Import ◽  
Mitochondrial Outer Membrane

scholarly journals Mutations in Fis1 disrupt orderly disposal of defective mitochondria

2014 ◽  
Vol 25 (1) ◽  
pp. 145-159 ◽  
Author(s):  
Qinfang Shen ◽  
Koji Yamano ◽  
Brian P. Head ◽  
Sumihiro Kawajiri ◽  
Jesmine T. M. Cheung ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Membrane Protein ◽  
Outer Membrane ◽  
Outer Membrane Protein ◽  
Couple Stress ◽  
Mitochondrial Fission ◽  
Mitochondrial Outer Membrane ◽  
Related Protein ◽  
Degradation Processes ◽  
Mitochondrial Toxins

Mitochondrial fission is mediated by the dynamin-related protein Drp1 in metazoans. Drp1 is recruited from the cytosol to mitochondria by the mitochondrial outer membrane protein Mff. A second mitochondrial outer membrane protein, named Fis1, was previously proposed as recruitment factor, but Fis1−/− cells have mild or no mitochondrial fission defects. Here we show that Fis1 is nevertheless part of the mitochondrial fission complex in metazoan cells. During the fission cycle, Drp1 first binds to Mff on the surface of mitochondria, followed by entry into a complex that includes Fis1 and endoplasmic reticulum (ER) proteins at the ER–mitochondrial interface. Mutations in Fis1 do not normally affect fission, but they can disrupt downstream degradation events when specific mitochondrial toxins are used to induce fission. The disruptions caused by mutations in Fis1 lead to an accumulation of large LC3 aggregates. We conclude that Fis1 can act in sequence with Mff at the ER–mitochondrial interface to couple stress-induced mitochondrial fission with downstream degradation processes.

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