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IMPORT OF CARBAMYLPHOSPHATE SYNTHETASE AND ORNITHINE TRANSCARBAMYLASE INTO MITOCHONDRIA OF RAT LIVER: DETECTION OF AGGREGATES OF ENZYME IN CYTOPLASM AND MITOCHONDRIA USING IMMUNOELECTRON MICROSCOPY WITH THE PROTEIN A‐GOLD METHOD
Author(s) -
Brands Ruud,
Hoogenraad Nicholas
Publication year - 1986
Publication title -
australian journal of experimental biology and medical science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.999
H-Index - 104
eISSN - 1440-1711
pISSN - 0004-945X
DOI - 10.1038/icb.1986.18
Subject(s) - ornithine transcarbamylase , endoplasmic reticulum , cytoplasm , mitochondrion , immunoelectron microscopy , enzyme , immunocytochemistry , biochemistry , biology , inner membrane , chemistry , microbiology and biotechnology , antibody , amino acid , urea cycle , endocrinology , arginine , immunology
Summary We investigated the distribution of the nuclear encoded mitochondrial enzymes, carbamylphosphate synthetase (CPS; EC 6.3.4.16) and ornithine transcarbamylase (OTC; EC 2.1.3.3) in liver by immunocytochemistry on ultrathin sections using the protein A‐gold technique. Both enzymes were found to be present as aggregates in the cytoplasm of hepatocytes, in association with ER membranes adjacent to mitochondria. Clusters of the enzymes were also found inside the mitochondria. The aggregation of these enzymes was found only with antibodies to CPS and OTC and not with antibodies against albumin or with IgG from unimmunized serum, nor were aggregates found in cells other than hepatocytes. The results are suggestive of localized uptake of clusters of enzyme or co‐translational uptake of enzyme at discrete localizations and that endoplasmic reticulum (ER) associations may be necessary for uptake of the precursor forms of CPS and OTC. The possible involvement is discussed of micropinosomes which are seen associated with inner membrane, intermembrane space and outer membrane in mitochrondria obtained from a perinuclear pellet where ER and mitochondria are frequently found in close association.