Preprotein translocase of the outer mitochondrial membrane: reconstituted Tom40 forms a characteristic TOM pore.
ABSTRACT Tom40 is the central pore-forming component of the translocase of the outer mitochondrial membrane (TOM complex). Different views exist about the secondary structure and electrophysiological characteristics of Tom40 from Saccharomyces cerevisiae and Neurospora crassa. We have directly compared expressed and renatured Tom40 from both species and find a high content of beta-structure in circular dichroism measurements in agreement with refined secondary structure predictions. The electrophysiological characterization of renatured Tom40 reveals the same characteristics as the purified TOM complex or mitochondrial outer membrane vesicles, with two exceptions. The total conductance of the TOM complex and outer membrane vesicles is twofold higher than the total conductance of renatured Tom40, consistent with the presence of two TOM pores. TOM complex and outer membrane vesicles possess a strongly enhanced sensitivity to a mitochondrial presequence compared to Tom40 alone, in agreement with the presence of several presequence binding sites in the TOM complex, suggesting a role of the non-channel Tom proteins in regulating channel activity.
- SourceAvailable from: José Miguel Alvarez-Suarez[Show abstract] [Hide abstract]
ABSTRACT: Mitochondria are essential organelles for cellular integrity and functionality mainteinance and their imparement is implicated in the development of a wide range of diseases, including metabolic, cardiovascular, degenerative and hyperproliferative pathologies. The identification of different compounds able to interact with mitochondria for therapeutic purposes is currently becoming of primary importance. Indeed, it is well kown that foods, particularly those of vegetable origin, present several constituents with beneficial effects on health. This review summarizes and updates the most recent findings concerning the mechanisms through which different dietary compounds from plant foods affect mitochondria functionality in healthy and pathological in vitro and in vivo models, paying particular attention to the pathways involved in mitochondrial biogenesis and apoptosis.Food and chemical toxicology: an international journal published for the British Industrial Biological Research Association 03/2014; · 2.99 Impact Factor
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ABSTRACT: Thirty-three years have elapsed since the first membrane protein (MP) was brought back in vitro to its native state starting from the completely unfolded polypeptide. Folding MPs is as useful from a practical point of view as it is thought-provoking from a theoretical one. Yet, this activity is considered as a high-risk, time-consuming endeavor, full of pitfalls, its path littered with the broken careers of graduate students sacrificed on the altar of a long shot that never paid off. In fact, a surprisingly high number of MPs have actually been folded or refolded in vitro. Analysis of the literature indicates i)that the endeavor is not as desperate as it may seem, ii)that techniques are diversifying and improving, and iii)that many MPs do not need the cellular biosynthetic apparatus, nor even a membrane environment, to reach a functional 3D structure. A compilation, hopefully close to complete, is presented of MPs that have been (re)folded in vitro to-date, with the conditions of their synthesis, the denaturant(s) used, if any, and the (re)folding conditions, along with a few comments. The hope is that this analysis will encourage membrane protein biochemists to consider producing their target proteins in this way, help them decide about an experimental course, and stimulate the reflection about which environments favor membrane protein folding and why.Archives of Biochemistry and Biophysics 07/2014; · 3.04 Impact Factor
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ABSTRACT: Membrane proteins play key roles in biology. Determination of their structure in a membrane environment, however, is highly challenging. To address this challenge, we developed an approach that couples hydrogen/deuterium exchange of membrane proteins to rapid unfolding and detection by solution-state NMR spectroscopy. We show that the method allows analysis of the solvent protection of single residues in liposome-embedded proteins such as the 349-residue Tom40, the major protein translocation pore in the outer mitochondrial membrane, which has resisted structural analysis for many years.PLoS ONE 11/2014; 9(11):e112374. · 3.53 Impact Factor