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Biology of the Metabolically Diverse Genus Gordonia. Matthias Arenskötter, 2004. Using Disulfide Bond Engineering To Study Conformational Changes in the ß'260-309 Coiled-Coil Region of Escherichia coli RNA Polymerase during  70 Binding.Larry C. Anthony, 2002.RNA polymerase of Escherichia coli is the sole enzyme responsible for mRNA synthesis in the cell . Upon binding of a sigma factor, the holoenzyme can direct transcription from specific promoter sequences . We have previously defined a region of the ß' subunit (ß'260-309, amino acids 260 to 309) which adopts a coiled-coil conformation shown to interact with 70 both in vitro and in vivo . However, it was not known if the coiled-coil conformation was maintained upon binding to
70 . In this work, we engineered a disulfide bond within ß'240-309 that locks the ß' coiled-coil region in the coiled-coil conformation, and we show that this "locked" peptide is able to bind to
70 . We also show that the locked coiled-coil is capable of inducing a conformational change within
70 that allows recognition of the -10 nontemplate strand of DNA . This suggests that the coiled-coil does not adopt a new conformation upon binding
70 or upon recognition of the -10 nontemplate strand of DNA .
Complete Polar Lipid Composition of Thermoplasma acidophilum HO-62 Determined by High-Performance Liquid Chromatography with Evaporative Light-Scattering Detection. Haruo Shimada, 2002.Polar ether lipids of Thermoplasma acidophilum HO-62 were purified by high-performance liquid chromatography with an evaporative light-scattering detector . Structures of purified lipids were investigated by capillary gas chromatography, mass spectrometry, and nuclear magnetic resonance . Three types of ether lipids were found: phospholipids, glycolipids, and phosphoglycolipids . The two phospholipids had glycerophosphate as the phosphoester moiety . The seven glycolipids had different combinations of gulose, mannose, and glucose, which formed mono- or oligosaccharides . The eight phosphoglycolipids with two polar head groups contained glycerophosphate as the phosphoester moiety and gulose alone or gulose and mannose, which formed mono- or oligosaccharides, as the sugar moiety . Although gulose is an unusual sugar in nature, several glyco- and phosphoglycolipids contained gulose as one of the sugar moieties in Thermoplasma acidophilum . All the ether lipids had isopranoid chains of C40 or C20 with zero to three cyclopentane rings . The structures of these lipids including four new glycolipids and three new phosphoglycolipids were determined, and a glycosylation process for biosynthesis of these glycolipids was suggested . A cka-gfp Transcriptional Fusion Reveals that the Colicin K Activity Gene Is Induced in Only 3 Percent of the Population. Janez Mulec, 2003.In prokaryotes, only a few examples of differential gene expression in cell populations have been described . Colicin production in natural populations of Escherichia coli, while providing a competitive advantage in the natural habitat, also leads to lysis of the toxin-producing cell . Colicin K synthesis has been found to be induced due to an increase in ppGpp (I . Kuhar, J . P . van Putten, D .  gur-Bertok, W . Gaastra, and B . J . Jordi, Mol . Microbiol . 41:207-216) . Using two transcriptional fusions, cka-gfp and cki-gfp, we show that at the single-cell level, the colicin K activity gene cka is expressed in only 3% of the bacterial population upon induction by nutrient starvation . In contrast, the immunity gene cki is expressed in the large majority of the cells . Expression of the cka-gfp fusion in a lexA-defective strain and in a relA spoT mutant strain indicates that differential expression of cka is established primarily at the level of transcription .
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