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Mitochondrial Precursor Proteins

Mitochondrial Precursor Proteins

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.
Most of the mitochondrial precursors...

Translocation of Proteins into the Mitochondria

Translocation of Proteins into the Mitochondria

Mitochondrial precursors are translocated to the internal subcompartments via independent mechanisms involving distinct protein machineries called translocases.
Sorting of outer membrane proteins:
Mitochondrial outer membrane proteins are of two types: the transmembrane, beta-barrel porins, and the membrane-anchored, alpha-helical proteins. Beta-barrel porin precursors are translocated by the TOM complex and inserted into the outer mitochondrial membrane by the SAM complex. In contrast,...

Mitochondrial Protein Sorting

Mitochondrial Protein Sorting

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...

Protein Transport into the Inner Mitochondrial Membrane

Protein Transport into the Inner Mitochondrial Membrane

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.
Transport of mitochondrial precursors across the TIM23 channel is driven by...

Structure of Porins

Structure of Porins

Mitochondria, chloroplasts, and gram-negative bacteria have transmembrane, beta-barrel proteins called porins to mediate the free diffusion of ions and metabolites across the membrane. Mitochondrial porin precursors contain conserved amino acid sequences called beta signals at their C-terminal. Beta signals have a motif of PoXGXXHyXHy (Po-Polar, X-Any amino acid, G-Glycine, Hy-LargeHydrophobic), which are crucial for precursor recognition to initiate precursor assembly. Beta-barrel precursors...

Site-Targeted Drug Delivery Systems: Polymeric Carriers

Site-Targeted Drug Delivery Systems: Polymeric Carriers

Polymeric carriers enhance targeted drug delivery by increasing efficacy while minimizing off-target effects. These carriers comprise a biodegradable polymeric backbone integrated with functional elements that enable targeting, improve physicochemical properties, and regulate drug release.Targeting MechanismsThe targeting ability of polymeric carriers is mediated by a homing device, which is a molecular recognition component designed to selectively bind to specific tissues or cells. Monoclonal...

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Related Experiment Video

Updated: Jun 1, 2026

Using Scaffold Liposomes to Reconstitute Lipid-proximal Protein-protein Interactions In Vitro

Using Scaffold Liposomes to Reconstitute Lipid-proximal Protein-protein Interactions In Vitro

Published on: January 11, 2017

Dimeric cationic amphiphilic polyproline helices for mitochondrial targeting.

Iris M Geisler¹, Jean Chmielewski

¹Department of Chemistry, Purdue University, 560 Oval Drive, West Lafayette, Indiana 47907, USA.

Pharmaceutical Research

|June 8, 2011

Summary

Dimerizing cationic amphiphilic polyproline helices (CAPHs) enhances cellular uptake and promotes direct cell transport, overcoming endosomal entrapment for improved biopolymer delivery with low toxicity.

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Area of Science:

Biochemistry
Cell Biology
Drug Delivery

Background:

Efficient delivery of therapeutic biopolymers across cell membranes is crucial but challenging.
Cell-penetrating peptides (CPPs) aid delivery but often face endosomal entrapment.
Cationic amphiphilic polyproline helices (CAPHs) are a class of CPPs with potential for improved delivery.

Purpose of the Study:

To optimize CAPHs for direct intracellular transport and mitochondrial localization.
To investigate the effect of CAPH dimerization on cellular uptake pathways.
To enhance the efficiency of biopolymer delivery across cell membranes.

Main Methods:

Studied the CAPH P11LRR, which utilizes both endocytotic and direct transport pathways.
Dimerized CAPH to assess enhancement of membrane association and direct transport.
Compared cellular uptake of monomeric and dimeric CAPH forms.

Main Results:

CAPH dimerization significantly increased cellular uptake compared to monomers.
Dimerization lowered the concentration threshold favoring direct cell transport.
Evidence of direct transport and mitochondrial localization of CAPH was observed.

Conclusions:

Peptide dimerization enhances CAPH cellular uptake efficiency.
Dimerization promotes direct cell entry at lower concentrations.
Optimized CAPH offers efficient delivery with low cell toxicity.