Jainkeene0121

Copyright © 2020 Cold Spring Harbor Laboratory Press; all rights reserved.Upstream Activation Factor (UAF) is a multifunctional transcription factor in Saccharomyces cerevisiae that plays dual roles in activating RNA Polymerase I (Pol I) transcription and repression of Pol II. For Pol I, UAF binds to a specific upstream element in the rDNA promoter and interacts with two other Pol I initiation factors, the TATA-Binding Protein (TBP) and Core Factor (CF). We used an integrated combination of chemical crosslinking mass spectrometry (CXMS), molecular genetics, protein biochemistry, and structural modeling to understand the topological framework responsible for UAF complex formation. Here, we report the molecular topology of the UAF complex, describe new structural and functional domains that play roles in UAF complex integrity, assembly, and biological function, and provides roles for previously identified UAF domains that include the Rrn5 SANT and Histone Fold domains. We highlight the role of new domains in Uaf30 that include an N-terminal Winged Helix domain and a disordered Tethering domain as well as a BORCS6-like domain found in Rrn9. Together, our results reveal a unique network of topological features that coalesce around a histone tetramer-like core to form the dual functioning UAF complex. Copyright © 2020 American Society for Microbiology.U6 snRNA is transcribed by RNA polymerase III (Pol III) and has an external upstream promoter that consists of a TATA sequence recognized by the TBP subunit of the Pol III basal transcription factor IIIB, and a proximal sequence element (PSE) recognized by the small nuclear RNA activating protein complex (SNAPc). Previously, we found that Drosophila melanogaster SNAPc (DmSNAPc) bound to the U6 PSE can recruit the Pol III general transcription factor Bdp1 to form a stable complex with the DNA. Here we show that DmSNAPc-Bdp1 can recruit TBP to the U6 promoter, and we identify a region of Bdp1 that is sufficient for TBP recruitment. Moreover, we find that this same region of Bdp1 cross-links to nucleotides within the U6 PSE at positions that also cross-link to DmSNAPc. Finally, cross-linking mass spectrometry reveals likely interactions of specific DmSNAPc subunits with Bdp1 and TBP. These data, together with previous findings, have allowed us to build a more comprehensive model of the DmSNAPc-Bdp1-TBP complex on the U6 promoter that includes nearly all of DmSNAPc, a portion of Bdp1, and the conserved region of TBP. Copyright © 2020 American Society for Microbiology.Microbial adhesion and biofilm formation are usually studied using molecular and cellular biology assays, optical and electron microscopy, or laminar flow chamber experiments. Today, atomic force microscopy (AFM) represents a valuable addition to these approaches, enabling the measurement of forces involved in microbial adhesion at the single-molecule level. In this Minireview, we discuss recent discoveries made applying state-of-the-art AFM techniques to microbial specimens in order to understand the strength and dynamics of adhesive interactions. These studies shed new light on the molecular mechanisms of adhesion, and demonstrate an intimate relationship between force and function in microbial adhesins. Copyright © 2020 American Society for Microbiology.Potassium and glutamate are the major cation and anion, respectively, in every living cell. Due to the high concentrations of both ions, the cytoplasm of all cells can be regarded as a potassium glutamate solution. This implies that the concentrations of both ions need to be balanced. While the control of potassium uptake by glutamate is well established for eukaryotic cells, much less is known about the mechanisms that link potassium homeostasis to glutamate availability in bacteria. Here, we have discovered that the availability of glutamate strongly decreases the minimal external potassium concentration required for the highly abundant Bacillus subtilis potassium channel KtrCD to accumulate potassium. In contrast, the inducible KtrAB and KimA potassium uptake systems have high apparent affinities for potassium even in the absence of glutamate. Experiments with mutant strains revealed that the KtrD subunit responds to the presence of glutamate. For full activity, KtrD synergistically requires the presence ohannel KtrCD is able to mediate potassium uptake at low external potassium concentration physiologically, the presence of glutamate results in a severely increased potassium uptake. Moreover, this is achieved by a mutation affecting the selectivity filter of the KtrD channel. These results highlight the integration between potassium and glutamate homeostasis in bacteria. Copyright © 2020 American Society for Microbiology.Multicellularity in Cyanobacteria played a key role in their habitat expansion contributing to the Great Oxidation Event around 2.45-2.32 billion years ago. Evolutionary studies have indicated that some unicellular cyanobacteria emerged from multicellular ancestors, yet little is known about how the emergence of new unicellular morphotypes from multicellular ancestors occurred. Our results give new insights into the evolutionary reversion from which the Gloeocapsopsis lineage emerged. Flow cytometry and microscopy results revealed morphological plasticity, involving patterned formation of multicellular morphotypes sensitive to environmental stimuli. Genomic analyses unveiled the presence of multicellular-associated genes in its genome. Calcein-FRAP experiments confirmed that Gloeocapsopsis sp. UTEXB3054 carry out cell-to-cell communication in multicellular morphotypes, but in slower timescales than filamentous cyanobacteria. Although traditionally classified as unicellular, our results suggest that Gloeocapsource acquisition and ecological relevance of this transient behavior are discussed. Copyright © 2020 American Society for Microbiology.5,10-Methylenetetrahydrofolate reductase (MetF/MTHFR) is an essential enzyme in one-carbon metabolism for de novo biosynthesis of methionine. Our in vivo and in vitro analyses of MSMEG_6664/MSMEI_6484, annotated as putative MTHFR in Mycobacterium smegmatis, failed to reveal their function as MTHFR. However, we identified two hypothetical proteins, MSMEG_6596 and MSMEG_6649 as noncanonical MTHFRs in the bacterium. MTHFRs are known to be oligomeric flavoproteins. Both MSMEG_6596 and MSMEG_6649 are monomeric proteins and lack flavin coenzymes. 2-NBDG molecular weight In vitro, the catalytic efficiency (k cat/K m) of MSMEG_6596 (MTHFR1) for 5,10-CH2-THF and NADH was ∼13.5 and 15.3 fold higher than that of MSMEG_6649 (MTHFR2). Thus, MSMEG_6596 is the major MTHFR. This interpretation was further supported by better rescue of E. coliΔmthfr by MTHFR1 than MTHFR2. As identified by LC-MS/MS, the product of MTHFR1 or MTHFR2 catalysed reactions was 5-CH3-THF. M. smegmatisΔmsmeg_6596 was partially auxotrophic for methionine and grew only poorly without methionine or without being complemented with a functional copy of MTHFR1 or MTHFR2.