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Related Concept Videos

Animal Mitochondrial Genetics02:59

Animal Mitochondrial Genetics

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Among all the organelles in an animal cell, only mitochondria have their own independent genomes. Animal mitochondrial DNA is a double-stranded, closed-circular molecule with around 20,000 base pairs. Mitochondrial DNA is unique in that one of its two strands, the heavy, or H, -strand is guanine rich, whereas the complementary strand is cytosine rich and called the light, or L, -strand. Compared to nuclear DNA, mitochondrial DNA has a very low percentage of non-coding regions and is marked by...
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Mitochondrial Protein Sorting01:39

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Mitochondria are double-membrane organelles of the eukaryotes involved in cellular metabolism, signaling, ATP synthesis, and programmed cell death.  Each of these processes requires specific proteins and enzymes that must be correctly sorted to the right mitochondrial subcompartment for the proper functioning of the organelle.
Most of these mitochondrial proteins are encoded by the nucleus and imported to the mitochondria as unfolded or loosely folded precursors. Mitochondrial precursors...
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Protein Transport into the Inner Mitochondrial Membrane01:34

Protein Transport into the Inner Mitochondrial Membrane

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Nuclear encoded mitochondrial precursors are imported to the inner membrane in a multistep process involving two separate translocons, TIM22 and TIM23. TIM23 is a cation-selective pore that remains closed by the N terminal segment of the protein. Negative charges on the TIM23 act as a receptor for the incoming precursor, pulling the positively charged matrix-targeting sequence for peptide insertion and translocation.
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Translocation of Proteins into the Mitochondria01:19

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Mitochondrial precursors are translocated to the internal subcompartments via independent mechanisms involving distinct protein machineries called translocases.
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Porin Insertion in the Outer Mitochondrial Membrane01:12

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Porins are beta-barrel proteins translocated to the mitochondrial outer membrane through the TOM complex into the intermembrane space. Porin precursors bind TIM chaperones within the intermembrane space and are guided to the Sorting and Assembly Machinery complex or SAM complex on the outer mitochondrial membrane.
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Mitochondrial Precursor Proteins01:39

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Mitochondrial precursors are partially unfolded or loosely folded polypeptide chains. Newly synthesized precursors are inhibited from spontaneously folding into their native conformation by the cytosolic chaperones, heat shock proteins 70 (Hsp70), and mitochondrial import stimulation factors (MSFs). Precursors bound to MSFs are guided to the TOM70-TOM37 receptors, while precursors bound to Hsp70  chaperones are targetted to TOM20-TOM22 receptor complexes.
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Author Spotlight: Advancing Techniques and Discoveries in Protein Synthesis and Assembly Through Innovative Mitochondrial Research
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Late Mitochondrial Acquisition, Really?

Mauro Degli Esposti1

  • 1Italian Institute of Technology, Genoa, Italy Centre for Genomic Sciences, UNAM Cuernavaca, Mexico mauro.degliesposti@iit.it mauro1italia@gmail.com.

Genome Biology and Evolution
|June 12, 2016
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This study critiques a recent paper suggesting a late origin for mitochondria. It demonstrates that the inferred bacterial ancestry of mitochondrial proteins is incorrect, challenging the late-origin hypothesis and supporting an early origin.

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Area of Science:

  • Evolutionary Biology
  • Cell Biology
  • Genomics

Background:

  • The origin of mitochondria is a fundamental question in eukaryote evolution.
  • A recent study proposed a late acquisition of mitochondria based on protein ancestry.
  • Mitochondria are essential organelles derived from endosymbiotic bacteria.

Purpose of the Study:

  • To critically evaluate the methodology and conclusions of Pittis and Gabaldón's recent Nature paper.
  • To re-examine the inferred bacterial ancestry of mitochondrial proteins.
  • To challenge the hypothesis of a late origin of mitochondria in eukaryote evolution.

Main Methods:

  • Phylogenetic analysis of mitochondrial protein sequences.
  • Comparative genomics to infer ancestral bacterial relationships.
  • Critique of previous bioinformatic approaches used in ancestry inference.

Main Results:

  • Inferred ancestry for numerous mitochondrial proteins was incorrectly assigned to non-aerobic proteobacteria.
  • The ancestral lineage of mitochondria is strongly linked to aerobic proteobacteria, not other bacterial groups.
  • The data refutes the claim that mitochondrial acquisition was a late event in eukaryote evolution.

Conclusions:

  • The original hypothesis of a late mitochondrial origin is not supported by robust phylogenetic evidence.
  • Mitochondrial proteins' ancestry points towards an early origin, consistent with established endosymbiotic theory.
  • This analysis provides a framework for future research into the precise evolutionary history of mitochondria.