Rajesh Nagarajan

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The reversible nucleophilic substitution reaction catalyzed by the vaccinia virus type IB topoisomerase has been investigated by measuring the equilibrium and rate effects of stereospecific sulfur substitution at the two nonbridging oxygen atoms of the attacked phosphodiester group. An energetic analysis of the combined effects of sulfur substitution and(More)
Members of the LuxI protein family catalyze synthesis of acyl-homoserine lactone (acyl-HSL) quorum sensing signals from S-adenosyl-L-methionine and an acyl thioester. Some LuxI family members prefer acyl-CoA, and others prefer acyl-acyl carrier protein (ACP) as the acyl-thioester substrate. We sought to understand the evolutionary history and mechanisms(More)
The bacterial D-alanyl-D-alanine transpeptidases (DD-peptidases) are the killing targets of beta-lactams, the most important clinical defense against bacterial infections. However, due to the constant development of antibiotic-resistance mechanisms by bacteria, there is an ever-present need for new, more effective antimicrobial drugs. While enormous numbers(More)
Good substrates of the Streptomyces R61 dd-peptidase, such as glycyl-L-alpha-amino-epsilon-pimelyl-D-alanyl-D-alanine, 1 (Anderson, J. W.; Pratt, R. F. Biochemistry 2000, 39, 12200-12209), contain the glycyl-L-alpha-amino-epsilon-pimelyl side chain. A number of thia variants of this structure have been synthesized by means of a disconnection strategy(More)
The Actinomadura R39 DD-peptidase catalyzes the hydrolysis and aminolysis of a number of small peptides and depsipeptides. Details of its substrate specificity and the nature of its in vivo substrate are not, however, well understood. This paper describes the interactions of the R39 enzyme with two peptidoglycan-mimetic substrates(More)
Proteins, nucleic acids, lipids, and various other smaller biomolecules are united by the presence of a common chemical entity of paramount and unique importancesthe phosphate ester. In proteins, phosphomonoester groups are added as reversible post-translational modifications to serine, threonine, or tyrosine amino acid side chains, and they serve as a(More)
The acyl-homoserine lactone (AHL) autoinducer mediated quorum sensing regulates virulence in several pathogenic bacteria. The hallmark of an efficient quorum sensing system relies on the tight specificity in the signal generated by each bacterium. Since AHL signal specificity is derived from the acyl-chain of the acyl-ACP (ACP = acyl carrier protein)(More)
Vaccinia type I DNA topoisomerase exhibits a strong site-specific ribonuclease activity when provided a DNA substrate that contains a single uridine ribonucleotide within a duplex DNA containing the sequence 5' CCCTU 3'. The reaction involves two steps: attack of the active site tyrosine nucleophile of topo I at the 3' phosphodiester of the uridine(More)
Vaccinia DNA topoisomerase (vTopo) is a prototypic eukaryotic type I topoisomerase that shows high specificity for nucleophilic substitution at a single phosphodiester linkage in the pentapyrimidine recognition sequence 5'-(C/T)+5 C+4 C+3 T+2 T+1 p / N(-1). This reaction involves reversible transesterification where the active site tyrosine of the enzyme(More)