scholarly journals Role of Pam16's degenerate J domain in protein import across the mitochondrial inner membrane

2005 ◽  
Vol 102 (35) ◽  
pp. 12419-12424 ◽  
Author(s):  
P. R. D'Silva ◽  
B. Schilke ◽  
W. Walter ◽  
E. A. Craig
Keyword(s):  
Protein Import ◽  
Inner Membrane ◽  
Mitochondrial Inner Membrane ◽  
J Domain

scholarly journals The J-related Segment of Tim44 Is Essential for Cell Viability: A Mutant Tim44 Remains in the Mitochondrial Import Site, but Inefficiently Recruits mtHsp70 and Impairs Protein Translocation

1999 ◽  
Vol 145 (5) ◽  
pp. 961-972 ◽  
Author(s):  
Alessio Merlin ◽  
Wolfgang Voos ◽  
Ammy C. Maarse ◽  
Michiel Meijer ◽  
Nikolaus Pfanner ◽  
...  
Keyword(s):  
Protein Import ◽  
Protein Translocation ◽  
Adaptor Protein ◽  
Dependent Manner ◽  
Wild Type ◽  
Yeast Saccharomyces Cerevisiae ◽  
Inner Membrane ◽  
Mitochondrial Inner Membrane ◽  
J Proteins

Tim44 is a protein of the mitochondrial inner membrane and serves as an adaptor protein for mtHsp70 that drives the import of preproteins in an ATP-dependent manner. In this study we have modified the interaction of Tim44 with mtHsp70 and characterized the consequences for protein translocation. By deletion of an 18-residue segment of Tim44 with limited similarity to J-proteins, the binding of Tim44 to mtHsp70 was weakened. We found that in the yeast Saccharomyces cerevisiae the deletion of this segment is lethal. To investigate the role of the 18-residue segment, we expressed Tim44Δ18 in addition to the endogenous wild-type Tim44. Tim44Δ18 is correctly targeted to mitochondria and assembles in the inner membrane import site. The coexpression of Tim44Δ18 together with wild-type Tim44, however, does not stimulate protein import, but reduces its efficiency. In particular, the promotion of unfolding of preproteins during translocation is inhibited. mtHsp70 is still able to bind to Tim44Δ18 in an ATP-regulated manner, but the efficiency of interaction is reduced. These results suggest that the J-related segment of Tim44 is needed for productive interaction with mtHsp70. The efficient cooperation of mtHsp70 with Tim44 facilitates the translocation of loosely folded preproteins and plays a crucial role in the import of preproteins which contain a tightly folded domain.

scholarly journals Mitochondrial Protein Import Motor: Differential Role of Tim44 in the Recruitment of Pam17 and J-Complex to the Presequence Translocase

2008 ◽  
Vol 19 (6) ◽  
pp. 2642-2649 ◽  
Author(s):  
Dana P. Hutu ◽  
Bernard Guiard ◽  
Agnieszka Chacinska ◽  
Dorothea Becker ◽  
Nikolaus Pfanner ◽  
...  
Keyword(s):  
Protein Import ◽  
Mitochondrial Protein ◽  
Adaptor Protein ◽  
Inner Membrane ◽  
Amino Terminal ◽  
Mitochondrial Inner Membrane ◽  
The Matrix ◽  
Yeast Mutants ◽  
Matrix Heat

The presequence translocase of the mitochondrial inner membrane (TIM23 complex) mediates the import of preproteins with amino-terminal presequences. To drive matrix translocation the TIM23 complex recruits the presequence translocase-associated motor (PAM) with the matrix heat shock protein 70 (mtHsp70) as central subunit. Activity and localization of mtHsp70 are regulated by four membrane-associated cochaperones: the adaptor protein Tim44, the stimulatory J-complex Pam18/Pam16, and Pam17. It has been proposed that Tim44 serves as molecular platform to localize mtHsp70 and the J-complex at the TIM23 complex, but it is unknown how Pam17 interacts with the translocase. We generated conditional tim44 yeast mutants and selected a mutant allele, which differentially affects the association of PAM modules with TIM23. In tim44-804 mitochondria, the interaction of the J-complex with the TIM23 complex is impaired, whereas unexpectedly the binding of Pam17 is increased. Pam17 interacts with the channel protein Tim23, revealing a new interaction site between TIM23 and PAM. Thus, the motor PAM is composed of functional modules that bind to different sites of the translocase. We suggest that Tim44 is not simply a scaffold for binding of motor subunits but plays a differential role in the recruitment of PAM modules to the inner membrane translocase.

scholarly journals Protein import into mitochondria: the requirement for external ATP is precursor-specific whereas intramitochondrial ATP is universally needed for translocation into the matrix.

1994 ◽  
Vol 5 (4) ◽  
pp. 465-474 ◽  
Author(s):  
C Wachter ◽  
G Schatz ◽  
B S Glick
Keyword(s):  
Protein Import ◽  
Protein Translocation ◽  
Mitochondrial Protein ◽  
Inner Membrane ◽  
In Vitro System ◽  
Mitochondrial Inner Membrane ◽  
Precursor Proteins ◽  
The Matrix

ATP is needed for the import of precursor proteins into mitochondria. However, the role of ATP and its site of action have been unclear. We have now investigated the ATP requirements for protein import into the mitochondrial matrix. These experiments employed an in vitro system that allowed ATP levels to be manipulated both inside and outside the mitochondrial inner membrane. Our results indicate that there are two distinct ATP requirements for mitochondrial protein import. ATP in the matrix is always needed for complete import of precursor proteins into this compartment, even when the precursors are presented to mitochondria in an unfolded conformation. In contrast, the requirement for external ATP is precursor-specific; depletion of external ATP strongly inhibits import of some precursors but has little or no effect with other precursors. A requirement for external ATP can often be overcome by denaturing the precursor with urea. We suggest that external ATP promotes the release of precursors from cytosolic chaperones, whereas matrix ATP drives protein translocation across the inner membrane.

scholarly journals Homologue replacement in the import motor of the mitochondrial inner membrane of trypanosomes

eLife ◽  
2020 ◽  
Vol 9 ◽  
Author(s):  
Corinne von Känel ◽  
Sergio A Muñoz-Gómez ◽  
Silke Oeljeklaus ◽  
Christoph Wenger ◽  
Bettina Warscheid ◽  
...  
Keyword(s):  
Trypanosoma Brucei ◽  
Driving Force ◽  
Protein Import ◽  
Normal Growth ◽  
Mitochondrial Proteins ◽  
Inner Membrane ◽  
Mitochondrial Inner Membrane ◽  
Bona Fide ◽  
J Domain ◽  
J Protein

Many mitochondrial proteins contain N-terminal presequences that direct them to the organelle. The main driving force for their translocation across the inner membrane is provided by the presequence translocase-associated motor (PAM) which contains the J-protein Pam18. Here, we show that in the PAM of Trypanosoma brucei the function of Pam18 has been replaced by the non-orthologous euglenozoan-specific J-protein TbPam27. TbPam27 is specifically required for the import of mitochondrial presequence-containing but not for carrier proteins. Similar to yeast Pam18, TbPam27 requires an intact J-domain to function. Surprisingly, T. brucei still contains a bona fide Pam18 orthologue that, while essential for normal growth, is not involved in protein import. Thus, during evolution of kinetoplastids, Pam18 has been replaced by TbPam27. We propose that this replacement is linked to the transition from two ancestral and functionally distinct TIM complexes, found in most eukaryotes, to the single bifunctional TIM complex present in trypanosomes.

scholarly journals Characterization of Mmp37p, aSaccharomyces cerevisiaeMitochondrial Matrix Protein with a Role in Mitochondrial Protein Import

2006 ◽  
Vol 17 (9) ◽  
pp. 4051-4062 ◽  
Author(s):  
Michelle R. Gallas ◽  
Mary K. Dienhart ◽  
Rosemary A. Stuart ◽  
Roy M. Long
Keyword(s):  
Matrix Protein ◽  
Protein Import ◽  
Mitochondrial Protein ◽  
Temperature Sensitive ◽  
Inner Membrane ◽  
Mitochondrial Inner Membrane ◽  
Close Proximity ◽  
The Matrix ◽  
Targeting Signal

Many mitochondrial proteins are encoded by nuclear genes and after translation in the cytoplasm are imported via translocases in the outer and inner membranes, the TOM and TIM complexes, respectively. Here, we report the characterization of the mitochondrial protein, Mmp37p (YGR046w) and demonstrate its involvement in the process of protein import into mitochondria. Haploid cells deleted of MMP37 are viable but display a temperature-sensitive growth phenotype and are inviable in the absence of mitochondrial DNA. Mmp37p is located in the mitochondrial matrix where it is peripherally associated with the inner membrane. We show that Mmp37p has a role in the translocation of proteins across the mitochondrial inner membrane via the TIM23-PAM complex and further demonstrate that substrates containing a tightly folded domain in close proximity to their mitochondrial targeting sequences display a particular dependency on Mmp37p for mitochondrial import. Prior unfolding of the preprotein, or extension of the region between the targeting signal and the tightly folded domain, relieves their dependency for Mmp37p. Furthermore, evidence is presented to show that Mmp37 may affect the assembly state of the TIM23 complex. On the basis of these findings, we hypothesize that the presence of Mmp37p enhances the early stages of the TIM23 matrix import pathway to ensure engagement of incoming preproteins with the mtHsp70p/PAM complex, a step that is necessary to drive the unfolding and complete translocation of the preprotein into the matrix.

scholarly journals Mitochondrial Membrane Dynamics—Functional Positioning of OPA1

Antioxidants ◽  
2018 ◽  
Vol 7 (12) ◽  
pp. 186 ◽  
Author(s):  
Hakjoo Lee ◽  
Yisang Yoon
Keyword(s):  
Mitochondrial Membrane ◽  
Proteolytic Cleavage ◽  
Membrane Dynamics ◽  
Mitochondrial Morphology ◽  
Inner Membrane ◽  
Mitochondrial Inner Membrane ◽  
Functional Differences ◽  
New Information ◽  
New Development

The maintenance of mitochondrial energetics requires the proper regulation of mitochondrial morphology, and vice versa. Mitochondrial dynamins control mitochondrial morphology by mediating fission and fusion. One of them, optic atrophy 1 (OPA1), is the mitochondrial inner membrane remodeling protein. OPA1 has a dual role in maintaining mitochondrial morphology and energetics through mediating inner membrane fusion and maintaining the cristae structure. OPA1 is expressed in multiple variant forms through alternative splicing and post-translational proteolytic cleavage, but the functional differences between these variants have not been completely understood. Recent studies generated new information regarding the role of OPA1 cleavage. In this review, we will first provide a brief overview of mitochondrial membrane dynamics by describing fission and fusion that are mediated by mitochondrial dynamins. The second part describes OPA1-mediated fusion and energetic maintenance, the role of OPA1 cleavage, and a new development in OPA1 function, in which we will provide new insight for what OPA1 does and what proteolytic cleavage of OPA1 is for.

scholarly journals The essential yeast protein MIM44 (encoded by MPI1) is involved in an early step of preprotein translocation across the mitochondrial inner membrane.

1993 ◽  
Vol 13 (12) ◽  
pp. 7364-7371 ◽  
Author(s):  
J Blom ◽  
M Kübrich ◽  
J Rassow ◽  
W Voos ◽  
P J Dekker ◽  
...  
Keyword(s):  
Protein Import ◽  
Early Stage ◽  
Proteolytic Processing ◽  
Early Step ◽  
Direct Role ◽  
Inner Membrane ◽  
Mitochondrial Inner Membrane ◽  
Preprotein Translocation ◽  
In Transit

The essential yeast gene MPI1 encodes a mitochondrial membrane protein that is possibly involved in protein import into the organelle (A. C. Maarse, J. Blom, L. A. Grivell, and M. Meijer, EMBO J. 11:3619-3628, 1992). For this report, we determined the submitochondrial location of the MPI1 gene product and investigated whether it plays a direct role in the translocation of preproteins. By fractionation of mitochondria, the mature protein of 44 kDa was localized to the mitochondrial inner membrane and therefore termed MIM44. Import of the precursor of MIM44 required a membrane potential across the inner membrane and involved proteolytic processing of the precursor. A preprotein in transit across the mitochondrial membranes was cross-linked to MIM44, whereas preproteins arrested on the mitochondrial surface or fully imported proteins were not cross-linked. When preproteins were arrested at two distinct stages of translocation across the inner membrane, only preproteins at an early stage of translocation could be cross-linked to MIM44. Moreover, solubilized MIM44 was found to interact with in vitro-synthesized preproteins. We conclude that MIM44 is a component of the mitochondrial inner membrane import machinery and interacts with preproteins in an early step of translocation.

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