Medizin - Open Access LMU - Teil 06/22

Successive translocation into and out of the mitochondrial matrix

We investigated the import and sorting pathways of cytochrome b2 and cytochrome c1, which are functionally located in the intermembrane space of mitochondria. Both proteins are synthesized on cytoplasmic ribosomes as larger precursors and are processed in mitochondria in two steps upon import. The precursors are first translocated across both mitochondrial membranes via contact sites into the matrix. Processing by the matrix peptidase leads to intermediate-sized forms, which are subsequently red...

Mitochondrial precursor proteins are imported through a hydrophilic membrane environment

We have analyzed how translocation intermediates of imported mitochondrial precursor proteins, which span contact sites, interact with the mitochondrial membranes. F1-ATPase subunit β(F1β) was trapped at contact sites by importing it into Neurospora mitochondria in the presence of low levels of nucleoside triphosphates. This F1β translocation intermediate could be extracted from the membranes by treatment with protein denaturants such as alkaline pH or urea. By performing import at low temperatu...

The carboxyl-terminal two-thirds of the ADP/ATP carrier polypeptide contains sufficient information to direct translocation into mitochondria

The precursor of the mitochondrial inner membrane protein ADP/ATP carrier is cytoplasmically synthesized without an amino-terminal peptide extension. We constructed a truncated precursor lacking the 103 amino acids from the amino terminus (about a third of the protein). Import of the truncated precursor into mitochondria showed the import characteristics of the authentic precursor, including nucleoside triphosphate dependence, requirement for a protease-sensitive component on the mitochondrial s...

Mitochondrial protein import

The precursor of F0-ATPase subunit 9 was bound to mitochondria in the absence of a mitochondrial membrane potential (delta psi). Binding was mediated by a protease-sensitive component on the mitochondrial surface. When delta psi was reestablished, bound precursor was directly imported without prior release from the mitochondrial membranes. A chimaeric protein consisting of the complete subunit 9 precursor fused to cytosolic dihydrofolate reductase (DHFR) was also specifically bound to mitochondr...

Mitochondrial porin of Neurospora crassa

cDNA encoding porin of Neurospora crassa, the major protein component of the outer mitochondrial membrane, was isolated and the nucleotide sequence was determined. The deduced protein sequence consists of 283 amino acids (29,979 daltons) and shows sequence homology of around 43% to yeast porin; however, no significant homology to bacterial porins was apparent. According to secondary structure predictions, mitochondrial porin consists mainly of membrane-spanning sided beta-sheets. Porin was effic...

High-affinity binding sites involved in the import of porin into mitochondria

The specific recognition by mitochondria of the precursor of porin and the insertion into the outer membrane were studied with a radiolabeled water-soluble form of porin derived from the mature protein. High-affinity binding sites had a number of 5-10 pmol/mg mitochondrial protein and a ka of 1-5 X 10(8) M-1. Binding was abolished after trypsin pretreatment of mitochondria indicating that binding sites were of protein-aceous nature. Specifically bound porin could be extracted at alkaline pH but ...

Antiepileptic drugs reduce serum uric acid

Uric acid examination in 554 epileptic out-patients under long-term anticonvulsant medication revealed significantly lower serum concentrations compared to a group of normal controls. In patients taking enzyme-inducing drugs, uric acid levels were found to be lower than in those under valproate sodium. In addition, uric acid concentrations showed a negative correlation with duration of therapy in epileptic males. At this time, we can only speculate on the mechanism involved in the reduction of u...

Deficiency in mRNA splicing in a cytochrome c mutant of neurospora crassa

Molecular cloning and characterization of cytochrome c cDNA clones of Neurospora crassa wild-type (74A) and a cytochrome c-deficient mutant (cyc1-1) are described. Southern blot analysis of genomic DNA indicates that only one cytochrome c gene exists in the N. crassa genome. The cDNA sequence of the wild-type cytochrome c confirmed the previously determined protein sequence. Sequence analysis of the cyc1-1 cDNA for cytochrome c revealed the presence of a larger open reading frame, owing to the p...

Characterization of Translocation Contact Sites Involved in the Import of Mitochondrial Proteins

Import of proteins into the mitochondrial matrix requires translocation across two membranes. Translocational intermediates of mitochondrial proteins, which span the outer and inner membrane simultaneously and thus suggest that translocation occurs in one step, have recently been described (Schleyer, M., and W. Neupert, 1985, Cell, 43:339-350). In this study we present evidence that distinct membrane areas are involved in the translocation process. Mitochondria that had lost most of their outer ...

Distinct steps in the import of ADP/ATP carrier into mitochondria

Transport of the precursor to the ADP/ATP carrier from the cytosol into the mitochondrial inner membrane was resolved into several consecutive steps. The precursor protein was trapped at distinct stages of the import pathway and subsequently chased to the mature form. In a first reaction, the precursor interacts with a protease-sensitive component on the mitochondrial surface. It then reaches intermediate sites in the outer membrane which are saturable and where it is protected against proteases...

Import of cytochrome c into mitochondria

The import of cytochrome c into mitochondria can be resolved into a number of discrete steps. Here we report on the covalent attachment of heme to apocytochrome c by the enzyme cytochrome c heme lyase in mitochondria from Neurospora crassa. A new method was developed to measure directly the linkage of heme to apocytochrome c. This method is independent of conformational changes in the protein accompanying heme attachment. Tryptic peptides of [35S]cysteine-labelled apocytochrome c, and of enzymat...

Translocation intermediates on the import pathway of proteins into mitochondria

Diagnostik der vaskulären Impotenz

Ureterstumpfmetastase eines Hypernephroms

Spongiosolysis

Organerhaltendes Vorgehen bei gutartigem Hodentumor?

Purification and Characterization of an Neutral Proteinase Inhibitor from Bovine Neutrophils

Pathobiochemische Mechanismen bei der Entzündung

Therapeutische Effekte der Inhibition lysosomaler Proteasen im Schock.

Zur Problematik der Bestimmung des Energieumsatzes im Labor und im Gelände

Schadstoffbelastung der Luft im Hochgebirge

Double labelling in situ hybridization using non-isotopic and isotopic detection

Gibt es eine zelltypspezifische Anordnung des Chromatins in Säugerzellkernen? Argumente von Ungläubigen, Agnostikern und Gläubigen.

In situ hybridization of chromosomes with biotinylated DNA after 1g sedimentation

Distances between two chromosomes in interphase nuclei as determined with digitized image analysis

Reaction pattern of alveolar cells in the posttraumatic lung failure

Influence of the lysosomal elastase inhibitor eglin on development of interstitial lung edema in E. coli bacteremia in pigs

Quantification of granulocyte enzymes/proteins with immunoassays

Studies of granulocyte function (chemiluminescence response) in postoperative infection

Feasibility study of very high aprotinin dosage in polytrauma patients