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Query: UNIPROT:P06889 (Mol)
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HgCl2 resistance (Hgr) in a strain of Pseudomonas putrefaciens isolated from the River Mersey was identified as plasmid-borne by its transfer to Escherichia coli in conjugative matings. This plasmid, pMERPH, could not be isolated and was incompatible with the chromosomally integrated IncJ Hgr plasmid R391. pMERPH and R391 both express inducible, narrow-spectrum mercury resistance and detoxify HgCl2 by volatilization. The cloned mer determinants from pMERPH (pSP100) and R391 (pSP200) have very similar restriction maps and express identical polypeptide products. However, these features show distinct differences from those of the Tn501 family of mer determinants. pSP100 and pSP200 failed to hybridize at moderate stringency to merRTPA and merC probes from Tn501 and Tn21, respectively. We conclude that the IncJ mer determinants are only distantly related to that from Tn501 and its closely homologous relatives and that it identifies a novel sequence which is relatively rare in bacteria isolated from natural environments.
Mol Gen Genet 1991 Aug
PMID:Novel mercury resistance determinants carried by IncJ plasmids pMERPH and R391. 188 14

Expression of the vitellogenin genes in avian and amphibian liver is regulated by estrogens. The DNA elements mediating estrogen induction of the various vitellogenin genes of chicken and Xenopus encompass one or more copies of a 13-mer palindromic sequence called the estrogen-responsive element (ERE). Here we show that upon incubation with the purified estrogen receptor (ER) from calf uterus the Xenopus vitellogenin A2 gene yields a DNase-I footprint over the ERE between -331 and -319. This element does not mediate the response to glucocorticoids or progestins in T47D cells. The three guanine residues in each half of the palindrome are protected against methylation by dimethylsulfate after incubation with ER, but not with glucocorticoid (GR) or progesterone (PR) receptors. In contrast, the chicken vitellogenin II gene exhibits multihormonal regulation by estrogens, progestins, and glucocorticoids in T47D and MCF7 cells. Regulation is mediated by the DNA region between -721 and -591 that contains four binding sites for hormone receptors, as demonstrated by DNase-I footprints and methylation protection experiments. The two distal and most proximal binding sites are recognized by ER, GR, and PR, whereas the central binding site is only bound by ER and GR. At suboptimal concentrations, estrogens and progestins or glucocorticoids act synergistically. In experiments using a DNA fragment containing an ERE adjacent to a glucocorticoid-responsive element/progesterone-responsive element, ER and PR bind synergistically to their corresponding sites, perhaps explaining the functional synergism of both hormones. Thus, two very different regulatory elements are used to mediate estrogen induction of related genes in chickens and amphibians.
Mol Endocrinol 1991 Mar
PMID:Hormonal regulation of vitellogenin genes: an estrogen-responsive element in the Xenopus A2 gene and a multihormonal regulatory region in the chicken II gene. 189 Sep 89

Electrophoretic evidence was obtained for two forms of pyrroline-5-carboxylate reductase (P5CR) in soybean nodules. One form was purified over 2300-fold. The apparent sizes of the polypeptides comprising the pyrroline-5-carboxylate reductases from soybean cytosol (29,700) and Escherichia coli (28,000) were consistent with those predicted from the sequences of the genes encoding them (Deutch et al., 1982 Nucleic Acid Res. 10, 7701-7714; Delauney and Verma, 1990 Mol. Gen. Genet. 221, 299-305). Primary structural analysis of the intact soybean P5CR subunit indicated that the amino-terminal residue is blocked. Analyses of a 12-mer and a 21-mer isolated from a cyanogen bromide digest were consistent with the proposition that the soybean P5CR isolated in these studies is very similar, although perhaps not identical, to the polypeptide predicted for the recently cloned soybean reductase (Delauney and Verma, 1990 Mol. Gen. Genet. 221, 299-305).
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PMID:Pyrroline-5-carboxylate reductase in soybean nodules: isolation/partial primary structure/evidence for isozymes. 189 34

Moraxella (Branhamella) catarrhalis is an aerobic Gram-negative diplococcus that is now recognized as a pathogen of the respiratory tract. Rapid and direct identification of this bacterium has become important to the clinical microbiology laboratory. Recently, rapid tests for the identification of Neisseria species and M. catarrhalis have been commercialized but they are primarily for Neisseriae; in these kits, M. catarrhalis is always identified presumptively. We have developed a DNA probe of chromosomal origin that is 100% specific for M. catarrhalis. The oligonucleotide probe was derived from a cloned Ase I chromosomal DNA fragment of M. catarrhalis that did not react with Haemophilus influenzae DNA in hybridization experiments. Three of the first 17 Ase I clones were selected randomly to be tested by colony hybridization against several different species that colonize the human respiratory tract. One of these three, pLQ121, has a 550 bp fragment inserted into pBR322 and was determined to be 100% specific to M. catarrhalis. This fragment was partially sequenced and a 30-mer oligonucleotide was synthesized from the sequence data. This probe was also shown to be 100% specific to the species.
Mol Cell Probes 1991 Feb
PMID:Development of a species-specific DNA probe for Moraxella (Branhamella) catarrhalis. 190 55

We have developed a 33 mer probe that hybridizes to the serine active site of the chromosomal ampC beta-lactamase gene of Pseudomonas aeruginosa and the Enterobacteriaceae. We tested this probe against a variety of Enterobacteriaceae, and a series of 23 P. aeruginosa by dot-blots and selected Southern blots. This probe is an alternative or supplement to enzyme studies for characterizing the class of a Gram-negative rod's beta-lactamase and is a useful tool for studies of Pseudomonas beta-lactamase regulation.
Mol Cell Probes 1991 Apr
PMID:A general ampC active site oligonucleotide probe for gram-negative rods. 190 78

The hypothesis that highly reiterated satellite DNAs in present-day populations evolve by molecular mechanisms that create, by saltatory amplification steps, new long arrays of satellite DNA, and that such long arrays are used for homogenization purposes, has been tested both in mouse and in humans. In mouse, the data obtained are consistent with this hypothesis. This was tested in more detail on chromosomes 13 and 21 of the human genome. A Centre d'Etudes du Polymorphisme Humain family, which in some individuals exhibits strong supplementary DNA bands following TaqI restriction endonuclease digestion and conventional gel electrophoresis, was analyzed by pulse field gel electrophoresis following restriction by BamHI. The supplementary bands on chromosome 13 (18 times the basic alpha satellite DNA repeat) and on chromosome 21 (a 9.5-mer) segregated with centromeric alpha satellite DNA blocks of 5 and 5.3 megabases, respectively. These are by far the largest alpha satellite block lengths seen in all chromosome 13 and chromosome 21 centromeric sequences so far analyzed in this manner. The possibility that these supplementary alpha satellite sequences were created in single individuals by saltatory amplification steps is discussed in light of our own data and that published by others. It is proposed that deletion events and unequal cross-overs, which both occur in large satellite DNA arrays, contribute to the homogenization of size and sequence of the alpha satellite DNA on most chromosomes of humans.
J Mol Evol 1991 Jul
PMID:On the mode of evolution of alpha satellite DNA in human populations. 190 75

Mismatch-specific enzymatic activity was sought for in nuclei from normal and transformed plant cells originating from tobacco (Nicotiana tabacum) callus and crown gall tumor induced by Agrobacterium tumefaciens. The specific enzymatic activity was assayed with substrates derived from synthetic oligonucleotides (19-mer sequences corresponding to the human K-ras gene). Single-base changes in the middle of the sequence were the basis for creating heteroduplexes with all eight mismatches. Homo- and heteroduplexes were ligated in a size ladder and used as substrates. We detected mismatch-specific DNA breakdown and determined basic requirements for the reactions. Kinetic analysis indicates the following reactivity order of preference: C:A=C:C=C:T greater than G:T approximately A:A approximately G:A approximately G:G approximately T:T much greater than G:C. It can be said now that specific mismatch recognition and repair activities have been detected in all kingdoms of living species.
Plant Mol Biol 1991 Oct
PMID:Mismatch-specific DNA breakdown in nuclear extract from tobacco (Nicotiana tabacum) callus. 191 2

Recently, P.A. Beal and P.B. Dervan, expanding on earlier observations by others, have established the formation of purine.purine.pyrimidine triple helices stabilized by G.GC, A.AT and T.AT base triples where the purine-rich third strand was positioned in the major groove of the Watson-Crick duplex and anti-parallel to its purine strand. The present nuclear magnetic resonance (n.m.r.) study characterizes the base triple pairing alignments and strand direction in a 31-mer deoxyoligonucleotide that intramolecularly folds to generate a 7-mer (R/Y-)n.(R+)n(Y-)n triplex with the strands linked by two T5 loops and stabilized by potential T.AT and G.GC base triples. (R and Y stand for purine and pyrimidine, respectively, while the signs establish the strand direction.) This intramolecular triplex gives well-resolved exchangeable and non-exchangeable proton spectra with Li+ as counterion in aqueous solution. These studies establish that the T1 to C7 pyrimidine and the G8 to A14 purine strands are anti-parallel to each other and align through Watson-Crick A.T and G.C pair formation. The T15 to G21 purine-rich third strand is positioned in the major groove of this duplex and pairs through Hoogsteen alignment with the purine strand to generate T.AT and G.GC triples. Several lines of evidence establish that the thymidine and guanosine bases in the T15 to G21 purine-rich third strand adopt anti glycosidic torsion angles under conditions where this strand is aligned anti-parallel to the G8 to A14 purine strand. We have also recorded imino proton n.m.r. spectra for an (R-)n.(R+)n(Y-)n triplex stabilized by G.GC and A.AT triples through intramolecular folding of a related 31-mer deoxyoligonucleotide with Li+ as counterion. The intramolecular purine.purine.pyrimidine triplexes containing unprotonated G.GC, A.AT and T.AT triples are stable at basic pH in contrast to pyrimidine.purine.pyrimidine triplexes containing protonated C+.GC and T.AT triples, which are only stable at acidic pH.
J Mol Biol 1991 Oct 20
PMID:Nuclear magnetic resonance structural studies of intramolecular purine.purine.pyrimidine DNA triplexes in solution. Base triple pairing alignments and strand direction. 194 59

Giardia lamblia telomeres have been isolated from a library enriched for repaired chromosome ends by (i) screening with a Plasmodium falciparum telomere and (ii) differential hybridization with Bal 31-digested and total G. lamblia DNA. Analysis of three clones isolated by this strategy has identified multiple tandem repeats of the 5-mer TAGGG. An oligonucleotide containing these repeats recognizes Bal 31-sensitive bands in Southern hybridizations and detects all G. lamblia chromosomes in pulsed-field gel electrophoresis separations. An abrupt transition from the G. lamblia rDNA sequence to telomeric repeats has been found in all three clones. In two of the clones the transition occurs at the same site, near the beginning of the large subunit rDNA sequence. In the third clone the transition occurs at a site in the intergenic spacer sequence between the rDNA genes. Hybridization of an rDNA probe to a pulsed-field separation of G. lamblia chromosomes indicates that rDNA genes are present on several chromosomes but vary in location from isolate to isolate. These results suggest that rRNA genes are clustered at telomeric locations in G. lamblia and that these clusters are mobile.
Mol Cell Biol 1991 Jun
PMID:Telomeric location of Giardia rDNA genes. 203 35

Continuous oxygen binding curves for two arthropodan hemocyanins were performed at different pH values ranging from 7.0 to 8.7 and in the presence of physiological concentrations of the bivalent ions Ca2+ and Mg2+. The arthropods Eurypelma californicum and Homarus americanus are classified as chelicerata and crustaceans, respectively. Their structurally well-characterized hemocyanins are composed of, in the case of E. californicum 24 subunits, and in the case of H. americanus 12 subunits. The role of protons as allosteric effectors of the oxygen binding was analysed in terms of the nesting model, which assumes hierarchies of allosteric equilibria that are based on obvious structural hierarchies. For each hemocyanin, the smallest structural repeating unit, the 12-mer or the 6-mer, respectively, was regarded as the "allosteric unit". Two allosteric units are allosterically coupled within the native molecules. The analysis revealed that in accordance with the postulations of the classical Monod-Wyman-Changeux model protons as allosteric effectors do not change the oxygen affinities of the four postulated conformations, but influence the allosteric equilibria between them at two different hierarchical levels. Model-independent determination of the affinity constants for the binding of the first and the last oxygen molecule to the native hemocyanins and to the isolated half-molecules confirmed the affinities calculated according to the nesting model. The stepwise establishment of new conformations during the assembly process from monomers to the structurally identical repeating unit and further on to the native molecule is shown. Possible physiological advantages of allosterically coupled allosteric units in contrast to allosterically uncoupled ones are thought to be (1) the option to regulate oxygen binding on different levels of structural hierarchy and (2) the increase of the oxygen-carrying capacity.
J Mol Biol 1990 Jan 05
PMID:Nested allostery of arthropodan hemocyanin (Eurypelma californicum and Homarus americanus). The role of protons. 215 35


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