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Bacterial Translocation and Protein Secretion01:26

Bacterial Translocation and Protein Secretion

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Bacterial protein secretion involves translocation systems to ensure proteins reach their designated locations, including the plasma membrane, periplasm, outer membrane, or the external environment. These translocation systems are vital for bacterial physiology, supporting processes like membrane assembly, enzymatic activity in the periplasm, and interactions with the external environment. The division of labor between Sec and Tat pathways ensures efficiency in handling proteins with diverse...
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Protein Transport to the Outer Chloroplast Membrane01:11

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Chloroplast outer membrane proteins encoded by the nucleus are synthesized in the cytosol. Soon after synthesis, they bind cytosolic factors such as 14-3-3 protein and the Hsp70 chaperones that keep these precursors in an unfolded state until their translocation.
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Protein Transport into the Inner Mitochondrial Membrane01:34

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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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Protein Transport to the Thylakoids01:22

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Thylakoids are membrane-bound sac-like structures within the chloroplast that serve as sites for photosynthesis. Thylakoid lumen contains many electron transport proteins and is enclosed by a thylakoid membrane rich in the light-harvesting complex. Proteins targeted to the thylakoids are transported as precursors and are sorted by the general TOC/TIC import pathway. Once the precursor reaches the stroma, stromal processing peptidases remove their transit signal and expose thylakoid signal...
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Translocation of proteins across membranes is an ancient process that occurs even in bacteria and archaebacteria. In fact, the components of the translocation machinery are still conserved between prokaryotes and eukaryotes.
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ATP-binding cassette or ABC transporter is the largest superfamily of integral membrane proteins. The transporters have transmembrane-binding domains (TMDs) and nucleotide-binding domains (NBDs). The TMDs are specific to their substrates, whereas the NBDs are similar to engines that complete ATP hydrolysis to complete the substrate transport. They can be full transporters consisting of two TMDs and NBDs, half transporters with one TMD and NBD, while some encoded with a single TMD or NBD are...
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TonB-Dependent Transport Across the Bacterial Outer Membrane.

Augustinas Silale1, Bert van den Berg1

  • 1Biosciences Institute, The Medical School, Newcastle University, Newcastle upon Tyne, United Kingdom; email: augustinas.silale@newcastle.ac.uk, bert.van-den-berg@newcastle.ac.uk.

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TonB-dependent transporters (TBDTs) in gram-negative bacteria use energy to import essential molecules. This review explores their complex transport mechanisms, potential in antibiotic delivery, and associated proteins.

Keywords:
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Area of Science:

  • Microbiology
  • Molecular Biology
  • Biochemistry

Background:

  • TonB-dependent transporters (TBDTs) are crucial for nutrient uptake across the outer membrane of gram-negative bacteria.
  • These transporters require energy from the proton motive force, supplied by the TonB-ExbBD complex.
  • The precise transport mechanism remains incompletely understood despite extensive research.

Purpose of the Study:

  • To review the current understanding of TBDT transport mechanisms.
  • To explore the potential of TBDTs for delivering novel antibiotics.
  • To highlight the role of TBDT-associated lipoproteins.

Main Methods:

  • Literature review of existing research on TonB-dependent transporters.
  • Analysis of studies on the energy-dependent transport mechanism.
  • Examination of research on antibiotic delivery via TBDTs.

Main Results:

  • TBDTs facilitate the uptake of scarce or large molecules otherwise unable to cross the outer membrane.
  • The energy-dependent transport involves intricate interactions between TBDTs and the TonB-ExbBD complex.
  • Associated lipoproteins play significant roles in TBDT function.

Conclusions:

  • TBDTs represent a complex and fascinating transport system in gram-negative bacteria.
  • Further research into TBDT mechanisms could unlock new strategies for antibiotic development.
  • Understanding TBDT-associated proteins is key to fully elucidating their function.