http://192.168.1.40:8080/xmlui/handle/123456789/1126 2026-05-31T14:02:57Z 2026-05-31T14:02:57Z Datta, I. Sau, Subrata Sil, A. K. Mandal, N. C. http://192.168.1.40:8080/xmlui/handle/123456789/2334 2013-03-22T10:08:02Z 2005-01-31T00:00:00Z

The bacteriophage lambda DNA replication protein P inhibits the oriC DNA- and ATP-binding functions of the DNA replication initiator protein DnaA of Escherichia coli Datta, I.; Sau, Subrata; Sil, A. K.; Mandal, N. C. Under the condition of expression of ?, P protein at lethal level, the oriC DNA-binding activity is significantly affected in wild-type E. coli but not in the rpl mutant. In purified system, the 2, P protein inhibits the binding of both oriC DNA and ATP to the wild-type DnaA protein but not to the rpl DnaA protein. We conclude that the X P protein inhibits the binding of oriC DNA and ATP to the wild-type DnaA protein, which causes the inhibition of host DNA synthesis initiation that ultimately leads to bacterial death. A possible beneficial effect of this interaction of X P protein with E. coli DNA initiator protein DnaA for phage DNA replication has been proposed.

2005-01-31T00:00:00Z Datta, I. Banik-Maiti, S. Adhikari, L. Sau, Subrata Das, N. Mandal, N. C. http://192.168.1.40:8080/xmlui/handle/123456789/2333 2013-03-22T09:28:18Z 2005-01-31T00:00:00Z

The mutation that makes Escherichia coli resistant to λ P gene-mediated host lethality is located within the DNA initiator gene dnaA of the bacterium Datta, I.; Banik-Maiti, S.; Adhikari, L.; Sau, Subrata; Das, N.; Mandal, N. C. Earlier, we reported that the bacteriophage lambda P gene product is lethal to Escherichia coli, and the E. coli rpl mutants are resistant to this lambda P gene-mediated lethality. In this paper, we show that under the lambda P gene-mediated lethal condition, the host DNA synthesis is inhibited at the initiation step. The rpl8 mutation maps around the 83 min position in the E. coli chromosome and is 94% linked with the dnaA gene. The rpl8 mutant gene has been cloned in a plasmid. This plasmid clone can protect the wild-type E. coli from lambda P gene-mediated killing and complements E. coli dnaAts46 at 42degreesC. Also, starting with the wild-type dnaA gene in a plasmid, the rpl-like mutations have been isolated by in vitro mutagenesis. DNA sequencing data show that each of the rpl8, rpl12 and rpl14 mutations has changed a single base in the dnaA gene, which translates into the amino acid changes N313T, Y200N, and S246T respectively within the DnaA protein. These results have led us to conclude that the rpl mutations, which make E. coli resistant to lambda P gene-mediated host lethality, are located within the DNA initiator gene dnaA of the host.

2005-01-31T00:00:00Z Ganguly, T. Chattoraj, P. Das, M. Chanda, P. K. Mandal, N. C. Lee, C.Y. Sau, Subrata http://192.168.1.40:8080/xmlui/handle/123456789/2330 2013-03-22T07:46:04Z 2004-11-30T00:00:00Z

A point mutation at the C-terminal half of the repressor of temperate mycobacteriophage L1 affects its binding to the operator DNA Ganguly, T.; Chattoraj, P.; Das, M.; Chanda, P. K.; Mandal, N. C.; Lee, C.Y.; Sau, Subrata The wild-type repressor CI of temperate mycobacteriophage Ll and the temperature-sensitive (ts) repressor CIts391 of a mutant Ll phage, L1cIts391, have been separately overexpressed in E. coli. Both these repressors were observed to specifically bind with the same cognate operator DNA. The operator-binding activity of CIts391 was shown to differ significantly than that of the CI at 32 to 42degreesC. While 40-95% operator-binding activity was shown to be retained at 35 to 42degreesC in CI, more than 75% operator-binding activity was lost in CIts391 at 35 to 38degreesC, although the latter showed only 10% less binding compared to that of the former at 32degreesC. The CIts391 showed almost no binding at 42degreesC. An in vivo study showed that the CI repressor inhibited the growth of a clear plaque former mutant of the Ll phage more strongly than that of the CIts391 repressor at both 32 and 42degreesC. The half-life of the CIts391-operator complex was found to be about 8 times less than that of the Cl-operator complex at 32degreesC. Interestingly, the repressor-operator complexes preformed at WC have shown varying degrees of resistance to dissociation at the temperatures which inhibit the formation of these complexes are inhibited. The CI repressor, but not that of CIts391, regains most of the DNA-binding activity on cooling to 32degreesC after preincubation at 42 to 52degreesC. All these data suggest that the 131(st) proline residue at the C-terminal half of CI, which changed to leucine in the CIts391, plays a crucial rote in binding the Ll repressor to the cognate operator DNA, although the helix-turn-helix DNA-binding motif of the Ll repressor is located at its N-terminal end.

2004-11-30T00:00:00Z Mandal, P. Chakraborty, P. Sau, Subrata Mandal, N.C. http://192.168.1.40:8080/xmlui/handle/123456789/2234 2013-03-14T11:46:10Z 2006-03-31T00:00:00Z

Purification and characterization of a deoxyriboendonuclease from Mycobacterium smegmatis Mandal, P.; Chakraborty, P.; Sau, Subrata; Mandal, N.C. A deoxyriboendonuclease has been purified to near homogeneity from a fast growing mycobacterium species, M. smegmatis and characterized to some extent. The size of enzyme is about 43 kDa as determined by a denaturing gel analysis. It shows optimum activity at 32 degrees C in Tris-HCl buffer (pH 7.2) containing 2.5 MM Of MgCl2. Both EDTA and K+ but not Na+ inhibit its activity. Evidences show that the enzyme is not a restriction endonuclease but catalyzes the endonucleolytic cleavage of both the double- as well as the single-strand DNA non-specifically. It has been shown that the cleavage by this enzyme generates DNA fragments carrying phosphate groups at 5' ends and hydroxyl group at the 3' ends, respectively. Analysis reveals that no endonuclease having size and property identical to our deoxyriboendonuclease had been purified from M. smegmatis before. The property of our enzymes closely matches with the deoxyriboendonucleases purified from diverse sources including bacteria.

2006-03-31T00:00:00Z