Role of ATP in mitochondrial protein import

The role of nucleoside triphosphates (NTPs) in the import of porin into the mitochondrial outer membrane was investigated with two forms of the porin precursor: the in vitro synthesized biosynthetic precursor (bs- porin) and a water-soluble form of porin (ws-porin) obtained by subjecting the membrane-derived porin to an acid-base treatment (exposure to trichloroacetic acid, followed by alkali and rapid neutralization). The import of ws-porin into mitochondria did not require NTPs, whereas the import of bs-porin required NTPs. In other characteristics, such as binding to a specific receptor protein on the mitochondrial surface, two-step insertion into the outer membrane, and formation of specific membrane channels, ws-porin was indistinguishable from bs-porin. Thus, the acid-base treatment applied in the preparation of ws-porin can substitute for the NTP-requiring step in mitochondrial protein import. We conclude that NTPs are required for unfolding mitochondrial precursor proteins ("translocation competent folding")

Identification of potential target genes for the tomato fruit-ripening regulator RIN by chromatin immunoprecipitation

<p>Abstract</p> <p>Background</p> <p>During ripening, climacteric fruits increase their ethylene level and subsequently undergo various physiological changes, such as softening, pigmentation and development of aroma and flavor. These changes occur simultaneously and are caused by the highly synchronized expression of numerous genes at the onset of ripening. In tomatoes, the MADS-box transcription factor RIN has been regarded as a key regulator responsible for the onset of ripening by acting upstream of both ethylene- and non-ethylene-mediated controls. However, except for <it>LeACS2</it>, direct targets of RIN have not been clarified, and little is known about the transcriptional cascade for ripening.</p> <p>Results</p> <p>Using immunoprecipitated (IPed) DNA fragments recovered by chromatin immunoprecipitation (ChIP) with anti-RIN antibody from ripening tomato fruit, we analyzed potential binding sites for RIN (CArG-box sites) in the promoters of representative ripening-induced genes by quantitative PCR. Results revealed nearly a 5- to 20-fold enrichment of CArG boxes in the promoters of <it>LeACS2</it>, <it>LeACS4</it>, <it>PG</it>, <it>TBG4</it>, <it>LeEXP1</it>, and <it>LeMAN4 </it>and of <it>RIN </it>itself, indicating direct interaction of RIN with their promoters <it>in vivo</it>. Moreover, sequence analysis and genome mapping of 51 cloned IPed DNAs revealed potential RIN binding sites. Quantitative PCR revealed that four of the potential binding sites were enriched 4- to 17-fold in the IPed DNA pools compared with the controls, indicating direct interaction of RIN with these sites <it>in vivo</it>. Near one of the four CArG boxes we found a gene encoding a protein similar to thioredoxin y1. An increase in the transcript level of this gene was observed with ripening in normal fruit but not in the <it>rin </it>mutant, suggesting that RIN possibly induces its expression.</p> <p>Conclusions</p> <p>The presented results suggest that RIN controls fruit softening and ethylene production by the direct transcriptional regulation of cell-wall-modifying genes and ethylene biosynthesis genes during ripening. Moreover, the binding of RIN to its own promoter suggests the presence of autoregulation for <it>RIN </it>expression. ChIP-based analyses identified a novel RIN-binding CArG-box site that harbors a gene associated with <it>RIN </it>expression in its flanking region. These findings clarify the crucial role of RIN in the transcriptional regulation of ripening initiation and progression.</p

Airy Notes Project: Creating Landscape Planning Method for the Ubicomp World

Abstract In this paper we introduce the collaborative project with researchers of ubiquitous computing and landscape planning aiming to create design method of landscape with environmental monitoring system

Production of overdense plasmas by launching 2,45 GHz electron cyclotron waves in a helical device

For production of low temperature plasmas with low collisionality, 2.45GHz microwave power up to 20kW is injected perpendicularly to the toroidal field at very low toroidal field BtComment: 12th International Congress on Plasma Physics, 25-29 October 2004, Nice (France