Die Proteinausstattung eines einzelnen pflanzlichen Mitochondriums

The structure and function of mitochondria have been characterized with increasing precision. How the protein inventory defines the characteristics of the organelle remains insufficiently understood, however. Recently we devised a quantitative proteomic approach to estimate the copy numbers of proteins in a single plant mitochondrion, as physical operational unit in the cell. We illustrate how such a simple thought experiment can give fascinating insights into how a mitochondrion works.

Prediction of thioredoxin and glutaredoxin target proteins by identifying reversibly oxidized cysteinyl residues

Summary A significant part of cellular proteins undergo reversible thiol-dependent redox transitions which often control or switch protein functions. Thioredoxins and glutaredoxins constitute two key players in this redox regulatory protein network. Both interact with various categories of proteins containing reversibly oxidized cysteinyl residues. The identification of thioredoxin/glutaredoxin target proteins is a critical step in constructing the redox regulatory network of cells or subcellular compartments. Due to the scarcity of thioredoxin/glutaredoxin target protein records in the public database, a tool called Reversibly Oxidized Cysteine Detector (ROCD) is implemented here to identify potential thioredoxin/glutaredoxin target proteins computationally, so that the in silico construction of redox regulatory network may become feasible. ROCD was tested on 46 thioredoxin target proteins in plant mitochondrion, and the recall rate was 66.7% when 50% sequence identity was chosen for structural model selection. ROCD will be used to predict the thioredoxin/glutaredoxin target proteins in human liver mitochondrion for our redox regulatory network construction project. The ROCD will be developed further to provide prediction with more reliability and incorporated into biological network visualization tools as a node prediction component. This work will advance the capability of traditional database- or text mining-based method in the network construction.

cis Recognition Elements in Plant Mitochondrion RNA Editing

ABSTRACT RNA editing in higher plant mitochondria modifies mRNA sequences by means of C-to-U conversions at highly specific sites. To determine thecis elements involved in recognition of an editing site in plant mitochondria, deletion and site-directed mutation constructs containing the cognate cox II mitochondrial gene were introduced into purified mitochondria by electroporation. The RNA editing status was analyzed for precursor and spliced transcripts from the test construct. We found that only a restricted number of nucleotides in the vicinity of the target C residue were necessary for recognition by the editing machinery and that the nearest neighbor 3′ residues were crucial for the editing process. We provide evidence that two functionally distinguishable sequences can be defined: the 16-nucleotide 5′ region, which can be replaced with the same region from another editing site, and a 6-nucleotide 3′ region specific to the editing site. The latter region may play a role in positioning the actual editing residue.