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Large Protein Complexes (large + protein_complex)
Selected AbstractsSetting and resetting of epigenetic marks in malignant transformation and developmentBIOESSAYS, Issue 8 2010Holger Richly Abstract Epigenetic modifications, such as DNA methylation and post-translation modifications of histones, have been shown to play an important role in chromatin structure, promoter activity, and cellular reprogramming. Large protein complexes, such as Polycomb and trithorax, often harbor multiple activities which affect histone tail modification. Nevertheless, the mechanisms underlying the deposition of these marks, their propagation during cell replication, and the alteration on their distribution during transformation still require further study. Here we review recent data on those processes in both normal and cancer cells, and we propose that the unscheduled expression of oncogenic transcription factors causes reprogramming of normal cells into cancer stem cells. [source] Dynein light chain family in Tetrahymena thermophilaCYTOSKELETON, Issue 2 2007David E. Wilkes Abstract Dyneins are large protein complexes that produce directed movement on microtubules. In situ, dyneins comprise combinations of heavy, intermediate, light-intermediate, and light chains. The light chains regulate the locations and activities of dyneins but their functions are not completely understood. We have searched the recently sequenced Tetrahymena thermophila macronuclear genome to describe the entire family of dynein light chains expressed in this organism. We identified fourteen genes encoding putative dynein light chains and seven genes encoding light chain-like proteins. RNA-directed PCR revealed that all 21 genes were expressed. Quantitative real time reverse transcription PCR showed that many of these genes were upregulated after deciliation, indicating that these proteins are present in cilia. Using the nomenclature developed in Chlamydomonas, Tetrahymena expresses two isoforms each of LC2, LC4, LC7, and Tctex1, three isoforms of p28, and six LC8/LC8-like isoforms. Tetrahymena also expresses two LC3-like genes. No Tetrahymena orthologue was found for Chlamydomonas LC5 or LC6. This study provides a complete description of the different genes and isoforms of the dynein light chains that are expressed in Tetrahymena, a model organism in which the targeted manipulation of genes is straightforward. Cell Motil. Cytoskeleton 2006. © 2006 Wiley-Liss, Inc. [source] Characterization of heterotrimeric G protein complexes in rice plasma membraneTHE PLANT JOURNAL, Issue 2 2004Chiyuki Kato Summary Two genes in the rice genome were identified as those encoding the , subunits, ,1 and ,2, of heterotrimeric G proteins. Using antibodies against the recombinant proteins for the ,, ,, ,1, and ,2 subunits of the G protein complexes, all of the subunits were proven to be localized in the plasma membrane in rice. Gel filtration of solubilized plasma membrane proteins showed that all of the , subunits were present in large protein complexes (about 400 kDa) containing the other subunits, ,, ,1, and ,2, and probably also some other proteins, whereas large amounts of the , and , (,1 and ,2) subunits were freed from the large complexes and took a 60-kDa form. A yeast two-hybrid assay and co-immunoprecipitation experiments showed that the , subunit interacted tightly with the ,1 and ,2 subunits, and so the , and , subunits appeared to form dimers in rice cells. Some dimers were associated with the , subunit, because few ,, ,1, and ,2 subunits were present in the 400-kDa complexes in a rice mutant, d1, which was lacking in the , subunit. When a constitutively active form of the , subunit was prepared by the exchange of one amino acid residue and introduced into d1, the mutagenized subunit was localized in the plasma membrane of the transformants and took a free, and not the 400-kDa, form. [source] Microreview: Type IV secretion systems: versatility and diversity in functionCELLULAR MICROBIOLOGY, Issue 9 2010Karin Wallden Summary Type IV secretion systems (T4SSs) are large protein complexes which traverse the cell envelope of many bacteria. They contain a channel through which proteins or protein,DNA complexes can be translocated. This translocation is driven by a number of cytoplasmic ATPases which might energize large conformational changes in the translocation complex. The family of T4SSs is very versatile, shown by the great variety of functions among family members. Some T4SSs are used by pathogenic Gram-negative bacteria to translocate a wide variety of virulence factors into the host cell. Other T4SSs are utilized to mediate horizontal gene transfer, an event that greatly facilitates the adaptation to environmental changes and is the basis for the spread of antibiotic resistance among bacteria. Here we review the recent advances in the characterization of the architecture and mechanism of substrate transfer in a few representative T4SSs with a particular focus on their diversity of structure and function. [source] | ||||||||||