56 research outputs found
The evolving story of the omega subunit of bacterial RNA polymerase
No full textOmega is the smallest subunit of bacterial RNA polymerase (RNAP). Although identified early in RNAP research, its function remained ambiguous and shrouded by controversy for a considerable period. It has subsequently been shown that the protein has a structural role in maintenance of the conformation of the largest subunit, \beta^', and recruitment of \beta^' to the enzyme assembly. Conservation of this function across all forms of life indicates the importance of its role. Several recent observations have suggested additional functional roles for this protein and have settled some long-standing controversies surrounding it. In this context, revisiting the \omega subunit story is especially interesting; here, we review the progress of \omega research since its discovery and highlight the importance of these recent observations
Deletion of the Gene rpoZ, Encoding the Subunit of RNA Polymerase, in Mycobacterium smegmatis Results in Fragmentation of the Subunit in the Enzyme Assembly
No full textA deletion mutation in the gene rpoZ of Mycobacterium smegmatis causes reduced growth rate and a change in colony morphology. During purification of RNA polymerase from the mutant strain, the subunit undergoes fragmentation but the fragments remain associated with the enzyme and maintain it in an active state until the whole destabilized assembly breaks down in the final step of purification. Complementation of the mutant strain with an integrated copy of the wild-type rpoZ brings back the wild-type colony morphology and improves the growth rate and activity of the enzyme, and the integrity of the subunit remains unaffected. DNA-dependent RNA polymerase (RNAP) is the central enzyme involved in gene expression and also constitutes a major target for genetic regulation (7, 8, 31). The bacterial RNAP core enzyme consists of four subunits: alpha (), beta (), beta () and omega () (21, 36). The subunit is the least well studied among all the subunits, though the subunit encoded by the rpoZ gene was proposed to be an integral part of the core RNAP several years ago (5, 10). In Escherichia coli is not found to be necessary for survival of the bacteriu
Rational design and synthesis of photo-responsive molecularly imprinted polymers for the enantioselective intake and release of l-phenylalanine benzyl ester on multiwalled carbon nanotubes
No full textDeletion of the Gene rpoZ, Encoding the \omega Subunit of RNA Polymerase, in Mycobacterium smegmatis Results in Fragmentation of the \beta ' Subunit in the Enzyme Assembly
No full textA deletion mutation in the gene rpoZ of Mycobacterium smegmatis causes reduced growth rate and a change in colony morphology. During purification of RNA polymerase from the mutant strain, the \beta'subunit undergoes fragmentation but the fragments remain associated with the enzyme and maintain it in an active state until the whole destabilized assembly breaks down in the final step of purification.Complementation of the mutant strain with an integrated copy of the wild-type rpoZ brings back the wild-type colony morphology and improves the growth rate and activity of the enzyme, and the integrity of the \beta' subunit remains unaffected
Isochronal annealing studies on 1.1 MeV Fe ion irradiated RAFM steel using variable energy slow positron beam
No full textDeletion of the rpoZ gene, encoding the subunit of RNA polymerase,results in pleiotropic surface related phenotypes in Mycobacterium smegmatis
No full textThe omega subunit, the smallest subunit of bacterial RNA polymerase, is known to be involved in maintaining the conformation of the beta' subunit and aiding its recruitment to the rest of the core enzyme assembly in Escherichia coli. It has recently been shown in Mycobacterium smegmatis, by creating a deletion mutation of the rpoZ gene encoding omega that the physiological role of the m subunit also includes providing physical protection to beta. Interestingly, the mutant had altered colony morphology. This paper demonstrates that the mutant mycobacterium has pleiotropic phenotypes including reduced sliding motility and defective biofilm formation.Analysis of the spatial arrangement of biofilms by electron microscopy suggests that the altered phenotype of the mutant arises from a deficiency in generation of extracellular matrix. Complementation of the mutant strain with a copy of the wild-type rpoZ gene integrated in the bacterial chromosome restored both sliding motility and biofilm formation to the wild-type state, unequivocally proving the role of omega in the characteristics observed for the mutant bacterium. Analysis of the cell wall composition demonstrated that the mutant bacterium had an identical glycopeptidolipid profile to the wild-type, but failed to synthesize the short-chain mycolic acids characteristic of biofilm growth in M. smegmati
Deletion of the rel gene in Mycobacterium smegmatis reduces its stationary phase survival without altering the cell-surface associated properties
No full textDormant or latent physiology of the mycobacterial species is a subject of current investigation in order to understand the long-term persistence of these organisms inside the host. It is argued that the carbon-starved mycobacteria may serve as a good model for the dormant bacilli. The relA/spoT gene is upregulated during carbon starvation in Mycobacterium tuberculosis and the deletion of the gene resulted in reduction of long-term persistence in M. tuberculosis. Overexpression of the gene in M. smegmatis changes the colony morphology of the bacteria. Here we show that knock-out of the relA/spoT gene compromises stationary-phase survival of M. smegmatis. However, the DeltarelA/spoT bacteria show similar profile of glycopeptidolipids as the wild-type bacteria under carbon starvation. We have seen here that M. smegmatis, a nonpathogenic species, upon carbon starvation exhibits reduced association with murine macrophage cell line RAW 264.7 in comparison to M. smegmatis grown in carbon-enriched medium. But the clearance of the a bacteria from macrophages takes place in the same window of time in both conditions
Lowest electronic states of neutral and ionic LiN
No full textWe have investigated the potential energy curves (PECs) of the LiN heteronuclear diatomic molecule, including its ionic species LiN+ and LiN−, using explicitly correlated multi-reference configuration interaction (MRCI-F12) calculations in conjunction with the correlation consistent quintuple- basis set. The effect of core–valence correlation, scalar relativistic effects, and the size of the basis sets has been investigated. A comprehensive set of spectroscopic constants determined based on the above-mentioned calculations are also reported for the lowest electronic states and all systems, including dissociation energies, harmonic and anharmonic vibrational frequencies, and rotational constants. Additional parameters, such as the dipole moments, equilibrium spin-orbit constants, excitation energies, and rovibrational energy levels, are also documented. We found that the three triplet states of LiN, namely, X 3∑−, A 3Π, and 2 3∑−, exhibit substantial potential wells in the PEC diagrams, while the quintet states are repulsive in nature. The ground state of the anion also shows a deep potential well in the vicinity of its equilibrium geometry. In contrast, the ground and excited states of the cation are very loosely bound. Charge transfer properties of each of these states are also analyzed to obtain an in-depth understanding of the interatomic interactions. We found that the core–valence correlation has a substantial effect on the calculated spectroscopic constants.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Atmospheric Remote Sensin
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