Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:6.5.1.2 (DNA ligase)
 2,749 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The yeast Kluyveromyces lactis synthesizes a beta-galactosidase (EC 3.2.1.32) which is inducible by lactose. We have isolated the gene that codes for this enzyme using recombinant DNA techniques. K. lactis DNA was partially digested with the restriction endonuclease Eco R1 and joined to Eco R1-digested pBR322 plasmid DNA using DNA ligase. ligase. A lac-mutant of Escherichia coli lacking the structural gene for beta-galactosidase was transformed with ligated DNA. Three lac+ transformants containing recombinant plasmids were selected. Two of the plasmids (pK15 and pK17) contain four Eco R1-K. lactis DNA fragments having molecular weights of 2.2, 1.4, 0.55 and 0.5 x 10(6) daltons. The other plasmid (pK16) lacks the smallest fragment. E. coli carrying any of these plasmids produce beta-galactosidase activity that has a sedimentation coefficient and immunological determinants that are nearly identical to K. lactis beta-galactosidase and distinctly different from E. coli beta-galactosidase. DNA-DNA hybridization studies show that the four Eco R1 fragments in pK15 hybridize to K. lactis but not to E. coli DNA.
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PMID:Molecular cloning and expression in E. coli of a yeast gene coding for beta-galactosidase. 10 Feb 26

The T4 polynucleotide ligase catalyzed joining of six chemically synthesized deoxypolynucleotides corresponding to lactose operator DNA has been investigated. Joining was studied using various combinations of segments. Joining reactions involving multiple sites and the formation of duplex operator DNA were complete in a few hours. Joining reactions involving a single site and the formation of only one strand of operator DNA required several days and repeated annealing in order to go to completion. These studies have permitted the synthesis on a preparative scale (several nanomoles) of operator duplexes and operator single strands.
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PMID:Studies on gene control regions. 2. Enzymatic joining of chemically synthesized lactose operator deoxyribonucleic acid segments. 85 79

Starting with one strand of the 40-bp synthetic operator (Sadler et al., 1978), we have constructed and cloned a 66-bp, palindromic DNA segment with the following sequence (Formula: see text), where the horizontal arrows indicate the locations of the two 21-bp "core" operator sequences in this segment and the vertical arrow designates the dyad axis of symmetry. Upon denaturation and rapid renaturation, each strand of this fragment forms a hairpin molecule still retaining an EcoRI cohesive end. Two hairpin molecules can be joined with T4 DNA ligase to form a duplex DNA molecule having no ends (dumbbell form A). Denaturation and rapid renaturation of dumbbell A yields a mixture of two dumbbell forms: dumbbell A which is a substrate for Eco RI, and a new form, dumbbell B, which is not a substrate. Each of the conformations of this DNA fragment have been purified and all are active in binding lactose repressor in vitro.
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PMID:Variants of a cloned synthetic lactose operator. I. A palindromic dimer lactose operator derived from one stand of the cloned 40-base pair operator. 701 67