This study determined whether muscle disuse affects mitochondrial protein import and whether changes in protein import are related to mitochondrial content and function. Protein import was measured using a model of unilateral peroneal nerve denervation in rats for 3 (n = 10), 7 (n = 12), or 14 (n = 14) days. We compared the import of preproteins into the matrix of subsarcolemmal (SS) and interm...

The essential gene TIM44 encodes a subunit of the inner mitochondrial membrane preprotein translocase that forms a complex with the matrix heat-shock protein Hsp70. The specific role of Tim44 in protein import has not yet been defined because of the lack of means to block its function. Here we report on a Saccharomyces cerevisiae mutant allele of TIM44 that allows selective and efficient inacti...

Expression of nuclear-encoded plastid proteins and import of those proteins into plastids are indispensable for plastid biogenesis. One possible cellular mechanism that coordinates these two essential processes is retrograde signaling from plastids to the nucleus. However, the molecular details of how this signaling occurs remain elusive. Using the plastid protein import2 mutant of Arabidopsis ...

Protein import into the nucleus and export from the nucleus are signal-mediated processes that require energy. The nuclear transport process about which the most information is currently available is classical nuclear localization signal (NLS)-mediated nuclear import. However, details concerning the signal-mediated export of proteins and RNAs as well as alternative nuclear import pathways are b...

Replication of human immunodeficiency virus type 1 (HIV-1) in non-dividing cells critically depends on import of the viral pre-integration complex into the nucleus. Genetic evidence suggests that viral protein R (Vpr) and matrix antigen (MA) are directly involved in the import process. An in vitro assay that reconstitutes nuclear import of HIV-1 pre-integration complexes in digitonin-permeabili...

Protein import into the peroxisome matrix is mediated by peroxisome-targeting signals (PTSs). We have developed a novel, quantitative, in vitro assay for measuring peroxisomal import of PTS1-containing proteins. This enzyme-linked immunosorbent assay-based system utilizes semi-intact human A431 cells or fibroblasts and a biotinylated version of the PTS1-containing import substrate, luciferase. ...

..................................................................................................................................... 4 List of Publications for the thesis............................................................................................. 5 Abbreviations .......................................................................................................................

Importin beta is a major mediator of import into the cell nucleus. Importin beta binds cargo molecules either directly or via two types of adapter molecules, importin alpha, for import of proteins with a classical nuclear localization signal (NLS), or snurportin 1, for import of m3G-capped U snRNPs. Both adapters have an NH2-terminal importin beta-binding domain for binding to, and import by, i...

The import of nucleus-encoded preproteins into plastids requires the coordinated activities of membrane protein complexes that facilitate the translocation of polypeptides across the envelope double membrane. Tic20 was identified previously as a component of the import machinery of the inner envelope membrane by covalent cross-linking studies with trapped preprotein import intermediates. To inv...

The precursor form of the major-harvesting chlorophyll a/b-binding protein @LHCP) of chloroplast thylakoids was overproduced in E. coli cells and used to study the influence of soluble factors on post-translational protein import into isolated pea chloroplasts. pLHCP solubilised in 8 M urea was not import-competent. However, if pLHCP was dialysed in the presence of soluble proteins (leaf extrac...