Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.2.1.17 (lysozyme)
 21,489 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Previous work from this laboratory has shown that the cytosine-containing T4 deoxyribonucleic acid (DNA) made by deoxycytidine triphosphatase (dCTPase) amber mutants is extensively degraded, and that nucleases controlled by genes 46 and 47 participate in this process. In this paper, we examine other consequences of a defective dCTPase. Included are studies of DNA synthesis and phage production, and of the control of both early and late protein synthesis after infection of Escherichia coli B with various T4 mutants defective in genes 56 (dCTPase), 42 (dCMP hydroxymethylase), 1 (deoxynucleotide kinase), 43 (DNA polymerase), 30 (polynucleotide ligase), 46 and 47 (DNA breakdown) or e(lysozyme). By varying the temperature of infection with a temperature-sensitive dCTPase mutant, we have been able to control intracellular dCTPase activity, and thus vary the cytosine content of the phage DNA. We have produced and characterized viable T4 phage in which cytosine replaces 20% of the 5-hydroxymethylcytosine (HMC) in the DNA. We present evidence which suggests that intact, cytosine-containing T4 DNA is much less efficient than is normal T4 DNA in directing the synthesis of tail-fiber antigen. Lysozyme production is much less affected by progressively decreasing dCTPase activity; however, complete substitution of cytosine is correlated with a depression of lysozyme synthesis greater than expected from the defective synthesis of DNA. Low but significant lysozyme synthesis is observed late after infection of E. coli B with T4 amber mutants defective in a number of genes controlling DNA synthesis. The "20% cytosine" T4 phage, once produced, can initiate an apparently normal infection at permissive temperatures; the synthesis of early enzymes, DNA, and phage does not appear to be impaired. Two roles for HMC in T4 DNA have been indicated previously: (i) involvement in host-controlled restriction of the phage, in which glucosylation of the hydroxymethyl group plays a crucial role (16, 29, 53, 58), and (ii) protection of vegetative DNA against phage-controlled nucleases, a protection not dependent on glucosylation (41, 66, 67). A third role is suggested by our present results: transcription of at least some late genes can occur only from HMC-containing DNA and not from cytosine-containing DNA.
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PMID:Biological effects of substituting cytosine for 5-hydroxymethylcytosine in the deoxyribonucleic acid of bacteriophage T4. 430 78

Bacteriophage phiYeO3-12 is a T7/T3-related lytic phage that naturally infects Yersinia enterocolitica serotype O:3 strains by using the lipopolysaccharide O polysaccharide (O antigen) as its receptor. The phage genome is a 39,600-bp-long linear, double-stranded DNA molecule that contains 58 genes. The roles of many of the genes are currently unknown. To identify nonessential genes, the isolated phage DNA was subjected to MuA transposase-catalyzed in vitro transposon insertion mutagenesis with a lacZ' gene-containing reporter transposon. Following electroporation into Escherichia coli DH10B and subsequent infection of E. coli JM109/pAY100, a strain that expresses the Y. enterocolitica O:3 O antigen on its surface, mutant phage clones were identified by their beta-galactosidase activity, manifested as a blue color on indicator plates. Transposon insertions were mapped in a total of 11 genes located in the early and middle regions of the phage genome. All of the mutants had efficiencies of plating (EOPs) and fitnesses identical to those of the wild-type phage when grown on E. coli JM109/pAY100. However, certain mutants exhibited altered phenotypes when grown on Y. enterocolitica O:3. Transposon insertions in genes 0.3 to 0.7 decreased the EOP on Y. enterocolitica O:3, while the corresponding deletions did not, suggesting that the low EOP was not caused by inactivation of the genes per se. Instead, it was shown that in these mutants the low EOP was due to the delayed expression of gene 1, coding for RNA polymerase. On the other hand, inactivation of gene 1.3 or 3.5 by either transposon insertion or deletion decreased phage fitness when grown on Y. enterocolitica. These results indicate that phiYeO3-12 has adapted to utilize Y. enterocolitica as its host and that these adaptations include the products of genes 1.3 and 3.5, DNA ligase and lysozyme, respectively.
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PMID:Nonessential genes of phage phiYeO3-12 include genes involved in adaptation to growth on Yersinia enterocolitica serotype O:3. 1568 5