Porins in mitochondria

Mitochondria import the vast majority of their proteins via dedicated protein machineries.

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.

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.

Inactivation of the Neurospora crassa mitochondrial outer membrane protein TOM70 by repeat-induced point mutation RIP causes defects in mitochondrial protein import and morphology. Cell— Acta—

Eukaryotic porin, also known as Voltage-Dependent Anion Channel VDAC , is the most frequent protein in the outer membrane of mitochondria that are responsible for cellular respiration. In accordance with the presumed ancestor, mitochondria are surrounded by two membranes. The mitochondrial outer membrane contains besides the eukaryotic porins responsible for its major permeability properties a variety of other not fully identified channels. It encloses also the TOM apparatus together with the sorting mechanism SAM, responsible for the uptake and assembly of many mitochondrial proteins that are encoded in the nucleus and synthesized in the cytoplasm at free ribosomes. The recognition and the study of electrophysiological properties of eukaryotic porin or VDAC started in the late seventies of the last century by a study of Schein et al. Whereas the literature about structure and function of eukaryotic porins was comparatively rare during the first 10years after the first study, the number of publications started to explode with the first sequencing of human Porin 31HL and the recognition of the important function of eukaryotic porins in mitochondrial metabolism.

Eukaryotic porin, also known as Voltage-Dependent Anion Channel VDAC , is the most frequent protein in the outer membrane of mitochondria that are responsible for cellular respiration. In accordance with the presumed ancestor, mitochondria are surrounded by two membranes. The mitochondrial outer membrane contains besides the eukaryotic porins responsible for its major permeability properties a variety of other not fully identified channels. It encloses also the TOM apparatus together with the sorting mechanism SAM, responsible for the uptake and assembly of many mitochondrial proteins that are encoded in the nucleus and synthesized in the cytoplasm at free ribosomes. The recognition and the study of electrophysiological properties of eukaryotic porin or VDAC started in the late seventies of the last century by a study of Schein et al. Whereas the literature about structure and function of eukaryotic porins was comparatively rare during the first 10years after the first study, the number of publications started to explode with the first sequencing of human Porin 31HL and the recognition of the important function of eukaryotic porins in mitochondrial metabolism. Many genomes contain more than one gene coding for homologs of eukaryotic porins. More than sequences of eukaryotic porins are known to date. Although the sequence identity between them is relatively low, the polypeptide length and in particular, the electrophysiological characteristics are highly preserved. This means that all eukaryotic porins studied to date are anion selective in the open state.

Porins in mitochondria

Federal government websites often end in. The site is secure. Eukaryotic porin, also known as Voltage-Dependent Anion Channel VDAC , is the most frequent protein in the outer membrane of mitochondria that are responsible for cellular respiration. In accordance with the presumed ancestor, mitochondria are surrounded by two membranes. The mitochondrial outer membrane contains besides the eukaryotic porins responsible for its major permeability properties a variety of other not fully identified channels. It encloses also the TOM apparatus together with the sorting mechanism SAM, responsible for the uptake and assembly of many mitochondrial proteins that are encoded in the nucleus and synthesized in the cytoplasm at free ribosomes. The recognition and the study of electrophysiological properties of eukaryotic porin or VDAC started in the late seventies of the last century by a study of Schein et al. Whereas the literature about structure and function of eukaryotic porins was comparatively rare during the first 10years after the first study, the number of publications started to explode with the first sequencing of human Porin 31HL and the recognition of the important function of eukaryotic porins in mitochondrial metabolism.

Noel.deyzel

To investigate the role of TOM complex components in porin insertion, we added excess amounts of a matrix-destined precursor protein to saturate import sites and then evaluated the effect on the import of porin into mitochondria in vitro. Selectivity changes in site-directed mutants of the VDAC ion channelstructural implications. Moreover, the porin precursor can be cross-linked to Tom20, Tom22, and Tom40 on its import pathway. Purification and characterization of Porin from corn Zea mays L. At voltages between 20mV and 30mV, the pores close more frequently but not too often, which means that the residual conductance associated with the closing pores could be estimated from the current recordings. Porin precursor accumulated at an intermediate stage of import could be cross-linked to Tom In cases where whole genome data are unavailable, it is not clear whether these represent allelic variants or different loci. Genomics-informed insights into endosymbiotic organelle evolution in photosynthetic eukaryotes. VDAC 2. Proof and evolutionary analysis of ancient genome duplication in the yeast Saccharomyces cerevisiae. Also potentially allied to each of these two groupings are monocot sequences.

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Purification and characterization of Porin from corn Zea mays L. Thornton, N. One question we tried to address in this analysis was the origin of VDAC paralogs. Table 1. No fossils of this organism are known but the comparison of the genomes of all modern organisms allowed the identification of a set of about genes, which could have been present in the LUCA Weiss et al. It was incorporated directly into intact mitochondria and not into rough endoplasmic reticulum Mihara et al. The smaller alignment was used in the Bayesian analysis that was very time consuming. Dynamics of the TOM complex of mitochondria during binding and translocation of preproteins. Sengers syndrome-associated mitochondrial acylglycerol kinase is a subunit of the human TIM22 protein import complex. Using these formulas, the structure of a porin can be determined by knowing only a few of the available parameters. Bayrhuber, M. Freitag, H.