Ligase bacterial

Bacterial cell wall synthesis inhibitor, d-ALANINE-d-ALANINE LIGASE BACTERIAL LEADER PEPTIDASE I Bacterial reorientation,... 

The synthetic and plasmid DNAs are mixed and join their sticky ends spontaneously. They are covalently bound together by DNA ligases, when the resulting hybrid plasmid is inserted into bacterial cells. Dilute calcium chloride solutions render the bacterial membranes permeable and allow the passage of ONA into the cells. 

Mycobacteria of the Mycobacterium avium complex are implicated in disseminated bacterial infections in AIDS patients. RFLP studies followed by hybridization with radiolabeled probe specific for an insertion sequence in M. avium (IS 1311) have been useful for typing M. avium stains (R2). A variety of molecular techniques are available for the diagnosis of Chlamydia trachomatis infection. In addition to PCR, a method based on the ligase chain reaction has also been found to be sensitive to the detection of C. trachomatis infection in urine specimens collected from male and female subjects (VI). The differentiation between low-risk genotypes of human papilloma virus (HPV 6 or 11) from genotypes of high... 

Conserved catalytic (adenylation) domain in NAD-dependent (bacterial) and ATP-dependent (archaeal-eukaryotic) DNA ligases (Aravind and Koonin, 1999) Conserved nucleotide joining-cleaving domain in type I and II topoisomerases, DnaG-type primases, OLD nucleases, and RecR (Toprim domain) (Aravind et al, 1998b)... 

For example, imagine that the DNA in a bacterium is damaged in some way—It may have been struck by an errant X-ray, for example. Without an intact, functioning DNA molecule, the bacterial cell will be unable to carry out its normal functions in the cell, and the bacterium may die. But evolution has developed a way of solving such problems. It has made available to the bacterial DNA certain kinds of enzymes—called ligases—whose job it is to search out and repair damaged sections of DNA. 

Cycloserine (Fig- 4) is produced by several species of Streptomyces. One of the basic glycosyl components of the bacterial cell wall, n-acetyl-muramic acid (the product of Mur A and MurB), is modified by the addition of the first three amino acids sequentially by MurC, MurD and MurE enzymes. A dipeptide, D-alanyl-D-alanine is then added to make the pentapeptide. In bacteria, L-alanine is the native form and it is converted to D-alanine form by alanine racemase (Air). Two D-alanines are joined by D-ala-D-ala ligase (DdlA) to synthesize the dipeptide. Cycloserine resembles the substrate for Air and Ddl and inhibits their respective reactions in stage I of the peptidoglycan biosynthesis (Fig. 2). 

This enzyme [EC 2.7.7.42], also known as glutamateiam-monia-ligase adenylyltransferase, plays a key role in controlling bacterial nitrogen metabolism by controlling the state of adenylylation of glutamine synthetase. 

Steps in the sealing of a DNA nick, catalyzed by DNA ligase. The bacterial ligase uses NAD+ to make an enzyme-AMP intermediate. Mammalian DNA ligases and bacteriophage T4 ligase use ATP for the same purpose. 

In cloning, the plasmid vector is incubated with a restriction endonuclease that cuts open the plasmid DNA. Exposure of the open DNA to a new DNA fragment plus a ligase reconstitutes the plasmid DNA with a new nucleotide sequence. The resulting recombinant DNA is inserted into bacterial cells, which then multiply. Each cell can contain 50-100 copies of the recombinant plasmid and can duplicate every 20-30 minutes. 

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