Pradeep Parrack

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The CIII protein encoded by the temperate coliphage lambda acts as an inhibitor of the ubiquitous Escherichia coli metalloprotease HflB (FtsH). This inhibition results in the stabilization of transcription factor lambdaCII, thereby helping the phage to lysogenize the host bacterium. LambdaCIII, a small (54-residue) protein of unknown structure, also(More)
HflX is a GTP binding protein of unknown function. Based on the presence of the hflX gene in hflA operon, HflX was believed to be involved in the lytic-lysogenic decision during phage infection in Escherichia coli. We find that E. coli HflX binds 16S and 23S rRNA - the RNA components of 30S and 50S ribosomal subunits. Here, using purified ribosomal(More)
The cyclic AMP receptor protein (CRP) from Escherichia coli, involved in the transcriptional regulation of a number of genes and operons, works by binding to specific sites upstream of promoters. CRP also binds cyclic AMP (cAMP), and this binding, which causes conformational changes in CRP, is mandatory for its activity. A cAMP-dependent variation in the(More)
Gal or Lac repressor binding to an upstream DNA segment, in the absence of DNA looping, represses the P1 promoter located on the same face and activates the P2 promoter situated on the opposite face of the DNA helix in the gal operon. Both inhibition and stimulation of transcription requires the physical presence of the C-terminal domain of the alpha(More)
A crucial element in the lysis-lysogeny decision of the temperate coliphage lambda is the phage protein CII, which has several interesting properties. It promotes lysogeny through activation of three phage promoters p(E), p(I) and p(aQ), recognizing a direct repeat sequence TTGCN6TTGC at each. The three-dimensional structure of CII, a homo-tetramer of 97(More)
The gal operon of Escherichia coli is negatively regulated by repressor binding to bipartite operators separated by 11 helical turns of DNA. Synergistic binding of repressor to separate sites on DNA results in looping, with the intervening DNA as a topologically closed domain containing the two promoters. A closed DNA loop of 11 helical turns, which is(More)
LambdaCII is the key protein that influences the lysis/lysogeny decision of lambda by activating several phage promoters. The effect of CII is modulated by a number of phage and host proteins including Escherichia coli HflK and HflC. These membrane proteins copurify as a tightly bound complex 'HflKC' that inhibits the HflB (FtsH)-mediated proteolysis of CII(More)
The temperate coliphage lambda, after infecting its host bacterium Escherichia coli, can develop either along the lytic or the lysogenic pathway. Crucial to the lysis/lysogeny decision is the homotetrameric transcription-activator protein CII (4 x 11 kDa) of the phage that binds to a unique direct-repeat sequence T-T-G-C-N6-T-T-G-C at each of the three(More)
The CIII protein of bacteriophage lambda exhibits antiproteolytic activity against the ubiquitous metalloprotease HflB (FtsH) of Escherichia coli, thereby stabilizing the lambdaCII protein and promoting lysogenic development of the phage. CIII also protects E.coli sigma(32), another substrate of HflB. We have recently shown that the protection of CII from(More)
The CII protein of bacteriophage lambda, which activates the synthesis of the lambda repressor, plays a key role in the lysis-lysogeny switch. CII has a small in vivo half-life due to its proteolytic susceptibility, and this instability is a key component for its regulatory role. The structural basis of this instability is not known. While studying(More)