Related Experiment Video
Updated: Sep 1, 2026

Optimized Protocol for the Extraction of Proteins from the Human Mitral Valve
Published on: June 14, 2017
The precursor to ornithine carbamyl transferase is transported to mitochondria as a 5S complex containing an import
Abstract:
The precursor to ornithine carbamyl transferase (Mr = 40,000) was synthesized in a rabbit reticulocyte lysate system and purified by immunoaffinity chromatography. Import of purified precursor by isolated mitochondria depended upon the presence of import factor(s) in fresh reticulocyte lysate. Velocity sedimentation analyses indicated that import factor binds to precursor to form a 5S complex (approximately 90 kDa); in this form, precursor was efficiently imported by isolated mitochondria. The ability of the 5S complex to deliver precursor into mitochondria was not affected by pretreatment with high concentrations of RNase. Import factor did not bind to mitochondria in the absence of precursor; upon binding of precursor to mitochondria in the presence of import factor, subsequent transmembrane uptake of precursor did not require the continued presence of additional lysate components.
Related Concept Videos
Mitochondrial Protein Sorting
Most of these mitochondrial proteins are encoded by the nucleus and imported to the mitochondria as unfolded or loosely folded precursors. Mitochondrial precursors...
Mitochondrial Precursor Proteins
Most of the mitochondrial precursors...
Translocation of Proteins into the Mitochondria
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,...
Protein Transport into the Inner Mitochondrial Membrane
Transport of mitochondrial precursors across the TIM23 channel is driven by...
Protein Transport to the Outer Chloroplast Membrane
Two models describe the mechanism of precursor recognition and entry across the outer membrane through the TOC complex. Model 1 suggests the newly synthesized precursor binds to the TOC receptor 159 and forms a complex.
Protein Transport to the Inner Chloroplast Membrane

