Porins in mitochondria

Mitochondria import the vast majority of their proteins via dedicated protein machineries. The translocase of the outer membrane TOM complex forms the porins in mitochondria entry site for precursor proteins that are produced on cytosolic ribosomes. Subsequently, different protein sorting machineries transfer the incoming preproteins to the mitochondrial outer and inner membranes, the intermembrane space, and the matrix.

Federal government websites often end in. The site is secure. Preview improvements coming to the PMC website in October Learn More or Try it out now. Porin, also termed the voltage-dependent anion channel, is the most abundant protein of the mitochondrial outer membrane.

Porins in mitochondria

Federal government websites often end in. The site is secure. Preview improvements coming to the PMC website in October Learn More or Try it out now. Mitochondrial porins, or voltage-dependent anion-selective channels VDAC allow the passage of small molecules across the mitochondrial outer membrane, and are involved in complex interactions regulating organellar and cellular metabolism. Numerous organisms possess multiple porin isoforms, and initial studies indicated an intriguing evolutionary history for these proteins and the genes that encode them. In this work, the wealth of recent sequence information was used to perform a comprehensive analysis of the evolutionary history of mitochondrial porins. Fungal porin sequences were well represented, and newly-released sequences from stramenopiles, alveolates, and seed and flowering plants were analyzed. A combination of Neighbour-Joining and Bayesian methods was used to determine phylogenetic relationships among the proteins. The aligned sequences were also used to reassess the validity of previously described eukaryotic porin motifs and to search for signature sequences characteristic of VDACs from plants, animals and fungi. Secondary structure predictions were performed on the aligned VDAC primary sequences and were used to evaluate the sites of intron insertion in a representative set of the corresponding VDAC genes. Our phylogenetic analysis clearly shows that paralogs have appeared several times during the evolution of VDACs from the plants, metazoans, and even the fungi, suggesting that there are no "ancient" paralogs within the gene family. Sequence motifs characteristic of the members of the crown groups of organisms were identified. The GLK and homologous or analogous motifs and the eukaryotic porin motifs in the four representative Chordates tend to be in exons that appear to have changed little during the evolution of these metazoans. In fact there is phase correlation among the introns in these genes.

What we know are the oldest fossils in the form of sedimentary rocks, known as stromatolites Margulis et al. Blachly-Dyson, E.

Porins are beta barrel proteins that cross a cellular membrane and act as a pore, through which molecules can diffuse. They are present in the outer membrane of gram-negative bacteria and some gram-positive mycobacteria mycolic acid-containing actinomycetes , the outer membrane of mitochondria , and the outer chloroplast membrane outer plastid membrane. This means that the nonpolar residues face outward so as to interact with the nonpolar lipids of outer membrane , whereas the polar residues face inwards into the center of the beta barrel to create the aqueous channel. The specific amino acids in the channel determine the specificity of the porin to different molecules. The individual strands are joined together by loops and turns. All porins form homotrimers in the outer membrane, meaning that three identical porin subunits associate together to form a porin super-structure with three channels.

Metrics details. Biological energy conversion in mitochondria is carried out by the membrane protein complexes of the respiratory chain and the mitochondrial ATP synthase in the inner membrane cristae. Recent advances in electron cryomicroscopy have made possible new insights into the structural and functional arrangement of these complexes in the membrane, and how they change with age. This review places these advances in the context of what is already known, and discusses the fundamental questions that remain open but can now be approached. Mitochondria are the powerhouses of the cell. In all eukaryotes that do not depend on photosynthesis, the mitochondria are the main source of adenosine triphosphate ATP , the energy-rich compound that drives fundamental cell functions. These functions include force generation for example, in muscle contraction and cell division , the biosynthesis, folding and degradation of proteins, and the generation and maintenance of membrane potentials. ATP is produced on a massive scale in the human body, amounting to 50 kg per day in a healthy adult, but considerably more in a long-distance runner.

Porins in mitochondria

Federal government websites often end in. The site is secure. Mitochondrial porins, or voltage-dependent anion-selective channels VDAC allow the passage of small molecules across the mitochondrial outer membrane, and are involved in complex interactions regulating organellar and cellular metabolism. Numerous organisms possess multiple porin isoforms, and initial studies indicated an intriguing evolutionary history for these proteins and the genes that encode them. In this work, the wealth of recent sequence information was used to perform a comprehensive analysis of the evolutionary history of mitochondrial porins. Fungal porin sequences were well represented, and newly-released sequences from stramenopiles, alveolates, and seed and flowering plants were analyzed. A combination of Neighbour-Joining and Bayesian methods was used to determine phylogenetic relationships among the proteins. The aligned sequences were also used to reassess the validity of previously described eukaryotic porin motifs and to search for signature sequences characteristic of VDACs from plants, animals and fungi. Secondary structure predictions were performed on the aligned VDAC primary sequences and were used to evaluate the sites of intron insertion in a representative set of the corresponding VDAC genes.

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The GLK and homologous or analogous motifs and the eukaryotic porin motifs in the Chordates tend to be in exons that appear to have changed little during the evolution of these metazoans. For cross-linking experiments, radiolabeled precursor was incubated with isolated outer membrane vesicles OMVs that were prepared according to Mayer et al. Orthologs, paralogs, and evolutionary genomics. In contrast, there are 32 phase 0, 24 phase 1, and 22 phase 2 introns in vertebrate VDAC paralogs; thus there is not a strong bias towards any one category of intron. Improving the prediction of protein secondary structure in three and eight classes using recurrent neural networks and profiles. The individual strands are joined together by loops and turns. Moreover, the porin precursor can be cross-linked to Tom20, Tom22, and Tom40 on its import pathway. Further sequence data will allow further refinement of these motifs, and data from organisms such as stramenopiles, will allow more complete analysis of this poorly-represented group. This result suggested again that the closed state s of mitochondrial porins is cation-selective, otherwise, the relatively small conductance difference for K-MES between open and closed state and the big difference for Tris-HCl cannot be understood. Results In this work, the wealth of recent sequence information was used to perform a comprehensive analysis of the evolutionary history of mitochondrial porins.

Mitochondria singular: mitochondrion are double membrane-bound cell organelles with a typical size of 0. They are found in most mammalian cells, with notable exceptions including mature erythrocytes.

Tom20 and Tom22 share the common signal recognition pathway in mitochondrial protein import. Mitochondria were isolated from the tom and tom strains as well as the corresponding wild-type. Google Scholar. Figure 8. When the OM fraction obtained by centrifugation steps was treated with detergent it showed pore-forming activity in artificial lipid bilayer membranes Roos et al. Broken outer membranes allow access of externally added proteinase K to the intermembrane space, thereby reducing the amount of CCHL. Generally, only substances less than daltons in size can diffuse through. Did VDAC gene duplications arise early in the evolution of the eukaryotes or did gene duplications occur independently in different evolutionary lineages? Biochem Cell Biol. Journal of Structural Biology. Regulation of mitochondrial protein import by cytosolic kinases.