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Tim50, a novel component of the TIM23 preprotein translocase of mitochondria.

ABSTRACT: The preprotein translocase of the inner membrane of mitochondria (TIM23 complex) is the main entry gate for proteins of the matrix and the inner membrane. We isolated the TIM23 complex of Neurospora crassa. Besides Tim23 and Tim17, it contained a novel component, referred to as Tim50. Tim50 spans the inner membrane with a single transmembrane segment and exposes a large hydrophilic domain in the intermembrane space. Tim50 is essential for viability of yeast. Mitochondria from cells depleted of Tim50 displayed strongly reduced import kinetics of preproteins using the TIM23 complex. Tim50 could be cross-linked to preproteins that were halted at the level of the translocase of the outer membrane (TOM complex) or spanning both TOM and TIM23 complexes. We suggest that Tim50 plays a crucial role in the transfer of preproteins from the TOM complex to the TIM23 complex through the intermembrane space.

SUBMITTER: Mokranjac D

PROVIDER: S-EPMC145450 | biostudies-literature | 2003 Feb

REPOSITORIES: biostudies-literature

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Tim50, a novel component of the TIM23 preprotein translocase of mitochondria.

Mokranjac Dejana D Paschen Stefan A SA Kozany Christian C Prokisch Holger H Hoppins Suzanne C SC Nargang Frank E FE Neupert Walter W Hell Kai K

The EMBO journal 20030201 4

The preprotein translocase of the inner membrane of mitochondria (TIM23 complex) is the main entry gate for proteins of the matrix and the inner membrane. We isolated the TIM23 complex of Neurospora crassa. Besides Tim23 and Tim17, it contained a novel component, referred to as Tim50. Tim50 spans the inner membrane with a single transmembrane segment and exposes a large hydrophilic domain in the intermembrane space. Tim50 is essential for viability of yeast. Mitochondria from cells depleted of T ...[more]

PMID: 12574118

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Diverse Functions of Tim50, a Component of the Mitochondrial Inner Membrane Protein Translocase.

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A mutagenesis analysis of Tim50, the major receptor of the TIM23 complex, identifies regions that affect its interaction with Tim23.

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The preprotein translocase YidC controls respiratory metabolism in Mycobacterium tuberculosis.

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Tim50's presequence receptor domain is essential for signal driven transport across the TIM23 complex.

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Cardiolipin mediates membrane and channel interactions of the mitochondrial TIM23 protein import complex receptor Tim50.

Project description:The phospholipid cardiolipin mediates the functional interactions of proteins that reside within energy-conserving biological membranes. However, the molecular basis by which this lipid performs this essential cellular role is not well understood. We address this role of cardiolipin using the multisubunit mitochondrial TIM23 protein transport complex as a model system. The early stages of protein import by this complex require specific interactions between the polypeptide substrate receptor, Tim50, and the membrane-bound channel-forming subunit, Tim23. Using analyses performed in vivo, in isolated mitochondria, and in reductionist nanoscale model membrane systems, we show that the soluble receptor domain of Tim50 interacts with membranes and with specific sites on the Tim23 channel in a manner that is directly modulated by cardiolipin. To obtain structural insights into the nature of these interactions, we obtained the first small-angle x-ray scattering-based structure of the soluble Tim50 receptor in its entirety. Using these structural insights, molecular dynamics simulations combined with a range of biophysical measurements confirmed the role of cardiolipin in driving the association of the Tim50 receptor with lipid bilayers with concomitant structural changes, highlighting the role of key structural elements in mediating this interaction. Together, these results show that cardiolipin is required to mediate specific receptor-channel associations in the TIM23 complex. Our results support a new working model for the dynamic structural changes that occur within the complex during transport. More broadly, this work strongly advances our understanding of how cardiolipin mediates interactions among membrane-associated proteins.

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Structural basis for the function of Tim50 in the mitochondrial presequence translocase.

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