Konstantin severinov biography of christopher

A principal result was the demonstration that dispensable regions could be involved in interactions with transcription factors. These results showed that RNA polymerase is a highly modular enzymes and opened several new avenues of research which are currently being pursued. The assembly-competent subunit fragments are being used to investigate intersubunit interactions during RNA polymerase assembly.

We use a unique genetic system that makes pol I dispensable for cell viability to uncover structure-functional relationships of this enzyme. In addition. Finally, in collaboration with a chemistry lab we are designing a general method of site-specific, chemical modification of proteins. Our data explain this anomaly, showing how the canonical HK97 fold has adapted to double the volume of the capsid, while maintaining its structural integrity.

Reconstructions of the procapsid and the expanded capsid defined the structure of the single vertex containing the portal protein. Together with a 1. These observations suggest a mechanism by which structural events inside the capsid can be communicated to the outside. Mol Cell. Epub Jan The introduction of azole heterocycles into a peptide backbone is the principal step in the biosynthesis of numerous compounds with therapeutic potential.

One of them is microcin B17, a bacterial topoisomerase inhibitor whose activity depends on the conversion of selected serine and cysteine residues of the precursor peptide to oxazoles and thiazoles by the McbBCD synthetase complex. Each McbB dimer clamps the N-terminal recognition sequence, while the C-terminal heterocycle of the modified peptide is trapped in the active site of McbC.

The McbD and McbC active sites are distant from each other, which necessitates alternate shuttling of the peptide substrate between them, while remaining tethered to the McbB dimer. An atomic-level view of the azole synthetase is a starting point for deeper understanding and control of biosynthesis of a large group of ribosomally synthesized natural products.

Single-nucleotide-resolution mapping of DNA gyrase cleavage sites across the Escherichia coli genome. Nucleic Acids Res. Xenogeneic Regulation of the Bacterial Transcription Machinery. J Mol Biol. The parasitic life cycle of viruses involves the obligatory subversion of the host's macromolecular processes for efficient viral progeny production. Viruses that infect bacteria, bacteriophages phages , are no exception and have evolved sophisticated ways to control essential biosynthetic machineries of their bacterial prey to benefit phage development.

The xenogeneic regulation of bacterial cell function is a poorly understood area of bacteriology. The activity of the bacterial transcription machinery, the RNA polymerase RNAP , is often regulated by a variety of mechanisms involving small phage-encoded proteins. In this review, we provide a brief overview of known phage proteins that interact with the bacterial RNAP and compare how two prototypical phages of Escherichia coli, T4 and T7, use small proteins to "puppeteer" the bacterial RNAP to ensure a successful infection.

Prokaryotes evolved numerous systems that defend against predation by bacteriophages. One class of such systems, named BREX, consists of a putative phosphatase, a methyltransferase and four other proteins. The induced phage DNA contains a methylated adenine residue in a specific motif. The same modification is found in the genome of BREX-carrying cells.

The results establish, for the first time, that immunity to BREX system defense is provided by an epigenetic modification. Biosynthesis of the RiPP trojan horse nucleotide antibiotic microcin C is directed by the N-formyl of the peptide precursor. Chem Sci. Post-translational modification on this ribosomally produced heptapeptide precursor is carried out by MccB, which consumes two equivalents of ATP to generate the N-P linkage.

We demonstrate that MccB only efficiently processes the precursor heptapeptide that retains the N -formylated initiator Met fMet. Binding studies and kinetic measurements evidence the role of the N -formyl moiety. Structural data show that the N -formyl peptide binding results in an ordering of residues in the MccB "crossover loop", which dictates specificity in homologous ubiquitin activating enzymes.

The N -formyl peptide exhibits substrate inhibition, and cannot be displaced from MccB by the desformyl counterpart. Such substrate inhibition may be a strategy to avert unwanted McC buildup and avert toxicity in the cytoplasm of producing organisms. CRISPR DNA arrays of unique spacers separated by identical repeats ensure prokaryotic immunity through specific targeting of foreign nucleic acids complementary to spacers.

However, acquisition of different PAM-associated spacers proceeds with markedly different efficiency from the same DNA. We found that during primed adaptation, efficiency of spacer acquisition is strongly negatively affected by the presence of an AAG trinucleotide-a consensus PAM-within the sequence being selected. No such trend is observed during naive adaptation.

The results are consistent with a unidirectional spacer selection process during primed adaptation and provide a specific signature for identification of spacers acquired through primed adaptation in natural populations. Different fragments are acquired into CRISPR arrays with widely different efficiencies, but the factors responsible are not known.

We analyzed the frequency of spacers acquired during primed adaptation in an E. These results are important because they provide new information on the mechanism of primed spacer acquisition. They add to other previous evidence in the field that pointed out to a "directionality" in the capture of new spacers. Our data strongly suggest that the recognition of an AAG PAM by the interference machinery components prior to spacer capture occludes downstream AAG sequences, thus preventing their recognition by the adaptation machinery.

Methods Enzymol. Epub Dec 1. The DNA interrogation and R-loop formation involve several distinct steps the molecular details of which are not fully understood. Defective transcription regulation is the common cause of aberrant growth and development and may result in malignant transformation. The long-term objective of our research is to uncover the molecular basis of transcription mechanism and regulation through structure-functional analysis of bacterial RNAP and associated proteins.

In addition, we use bacteriophage development as a model system to study temporal regulation of gene expression and to uncover novel mechanisms of transcription regulation. We also study microcins, small ribosomally-synthesized inhibitors of bacterial growth. Genomic sequences of several novel bacteriophages have been determined and host RNAP binding transcription factors encoded by these phages have been identified.

Konstantin severinov biography of christopher

The molecular mechanisms of these factors function, and the structural aspects of their interaction with RNAP have been studied. Analysis of phage-host interaction has taken a new direction in , concentrating on a novel mechanism of bacterial resistance to phages -- through the action of CRISPR system. We continued our studies of various aspects of bacterial RNAP structure and function.