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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The DNA sequences of the mercuric resistance determinants of plasmid R100 and transposon Tn501 distal to the gene (merA) coding for mercuric reductase have been determined. These 1.4 kilobase (kb) regions show 79% identity in their nucleotide sequence, and in both sequences two common potential coding sequences have been identified. In R100, the end of the homologous sequence is disrupted by an 11.2 kb segment of DNA which encodes the sulfonamide and streptomycin resistance determinants of Tn21. This insert contains terminal inverted repeat sequences and is flanked by a 5 base pair (bp) direct repeat. The first of the common potential coding sequences is likely to be that of the merD gene. Induction experiments and mercury volatilization studies demonstrate an enhancing but non-essential role for these merA-distal coding sequences in mercury resistance and volatilization. The potential coding sequences have predicted codon usages similar to those found in other Tn501 and R100 mer genes.
Mol Gen Genet 1986 Jan
PMID:The nucleotide sequence of the mercuric resistance operons of plasmid R100 and transposon Tn501: further evidence for mer genes which enhance the activity of the mercuric ion detoxification system. 300 31

Comparison of physical maps of the broad host range plasmids R751, R906 and R772, belonging to the IncP beta sub-group of the Escherichia coli incompatibility group P, reveals two large regions of similarity, separated by dissimilar regions which contain the majority of the cleavage sites for restriction endonucleases with hexanucleotide recognition sites. Mapping of the regions of these plasmids which show homology to probes specific for genetically characterised segments of the distantly related IncP alpha plasmid RK2, involved in plasmid maintenance or conjugal transfer, reveals that all four plasmids share a similar genetic organisation. In each case the homologous plasmid backbone is interrupted by heterologous segments both between the essential replication loci oriV and trfA, and between the conjugal transfer regions tra1 and tra2, although in the case of R772 the segment of the backbone carrying the trfA and tra2 regions is inverted relative to that of the other plasmids. However, in the case of pJP4, shown to be a fourth member of the IncP beta sub-group, the backbone is interrupted only by a single large segment adjacent to the trfA region. Mapping of the regions of the four IncP beta plasmids which show homology to Tn501 and nucleotide sequence determination at the ends of the homologous regions reveals that R906, R772 and pJP4 share a common mercury resistance region. This region, which appears to have been inactivated in R772, was probably inserted into a common ancestor of these plasmids by the transposition of an element related to an ancestor of Tn501. R751 shows no trace of the mercury resistance region, but contains a short relict of Tn501, derived from an independent insertion event.
Mol Gen Genet 1987 Mar
PMID:Comparison of the organisation of the genomes of phenotypically diverse plasmids of incompatibility group P: members of the IncP beta sub-group are closely related. 303 42

By using a protein-DNA cross-linking method (D. S. Gilmour and J. T. Lis, Mol. Cell. Biol. 5:2009-2018, 1985), we examined the in vivo distribution of RNA polymerase II on the hsp70 heat shock gene in Drosophila melanogaster Schneider line 2 cells. In heat shock-induced cells, a high level of RNA polymerase II was detected on the entire gene, while in noninduced cells, the RNA polymerase II was confined to the 5' end of the hsp70 gene, predominantly between nucleotides -12 and +65 relative to the start of transcription. This association of RNA polymerase II was apparent whether the cross-linking was performed by a 10-min UV irradiation of chilled cells with mercury vapor lamps or by a 40-microsecond irradiation of cells with a high-energy xenon flash lamp. We hypothesize that RNA polymerase II has access to, and a high affinity for, the promoter region of this gene before induction, and this poised RNA polymerase II may be critical in the mechanism of transcription activation.
Mol Cell Biol 1986 Nov
PMID:RNA polymerase II interacts with the promoter region of the noninduced hsp70 gene in Drosophila melanogaster cells. 309 67

Mercury resistant soil and intestinal bacteria were isolated from different mercury deposit areas of the USSR. Mercury reductases from all gram negative bacteria studied (Pseudomonas, Acinetobacter and Enterobacterial species) with a single exception (Flavobacterium sp.) were immunologically cross reactive. Two immunological types of mercury reductases were found among gram positive bacteria (Bacillus, Staphylococcus and Coryneform species). Further subdivisions were done by "spur" formation tests. Despite considerable diversity of mercury reductases revealed in this study, we found several strains which belonged to distant genera but contained immunologically indistinguishable enzymes. This suggested that the horizontal spread of the corresponding genes occurred in these genera in relatively recent time.
Mol Gen Mikrobiol Virusol 1988 Dec
PMID:[Study of the horizontal transfer of mercury resistance genes in natural populations of bacteria using antibodies to mercury reductases]. 315 Jul 70

Most of bacterial cells in soil samples taken from a mine at the Khaidarkan mercury-antimony deposit (Kirghiz SSR) proved to contain R-plasmids with determinants of mercury resistance (HgCl2). Plasmids had a high molecular mass (approximately 10(8], though some deviated substantially from this size; at least part of them were transmissible. Many Hgr bacteria also showed an increased resistance to antimony (SbCl3), but no relation could be found between this character and the plasmids. Bacteria from soil samples taken at different distances from the mine were virtually devoid of Hgr plasmids: saturation of bacteria with Hgr factors is maintained by selective pressure action only within regions with high concentration of poison. Hgr plasmids at the Khaidarkan deposit were also found in enteric bacteria isolates from the gut of Mus musculus mice and Bufo viridis toads. Some bacterial plasmids from animals carried, apart from Hgr, antibiotic resistance determinants (Tcr, Cmr, Smr), i.e. were multiple resistance factors. These plasmids often displayed intrinsic instability and lost resistance determinants when conjugationally transferred to some E. coli strains.
Mol Biol (Mosk)
PMID:[R-factors of mercury resistance in bacteria isolated in the mercury-antimony deposit region]. 315 3

The preparation, spectroscopic investigation, structure determination, conformational analysis, and modeling of the Dewar pyrimidinone photoproduct of thymidylyl-(3'----5')-thymidine, previously referred to as TpT3 [Johns, H. E., Pearson, M. L., LeBlanc, J. C., & Heilleiner, C. W. (1964) J. Mol. Biol. 9, 503-524], is described. TpT3 was prepared in quantitative yield by photolysis of an aqueous solution of the (6-4) photoproduct of TpT with Pyrex-filtered medium-pressure mercury arc light. TpT3 was analyzed by FAB MS, IR, UV, and 1H, 13C, and 31P NMR spectroscopy. The spectroscopic data led to the conclusion that TpT3 results from the photoisomerization of the pyrimidinone ring of the (6-4) product of TpT to its Dewar valence isomer. Torsion angle and interproton distance information derived from coupling constants and NOE data was used to constrain ring conformation searches by utilizing the SYBYL molecular modeling program subroutine SEARCH. Sets of angles derived from the ring search procedure were then used to construct structures whose geometries were optimized by the energy-minimization subroutine MAXIMIN. A two-state model for the solution-state structure of the Dewar photoproduct was chosen which was energetically sound, fit the experimental coupling constants with an RMS deviation of 1.15 Hz, and was consistent with the NOE data. The model for the Dewar photoproduct was compared to a model for the (6-4) photoproduct and the TpT subunits of the Dickerson dodecamer structure by a least-squares fitting procedure. It was concluded that the Dewar photoproduct more closely resembles a B-form TpT unit than does the (6-4) photoproduct.
 ...
PMID:Solution-state structure of the Dewar pyrimidinone photoproduct of thymidylyl-(3'----5')-thymidine. 320 70

The acyl ester bond between the third complement protein, C3, and a variety of molecules is hydrolyzed spontaneously at neutral pH (Venkatesh et al., 1984). Modification of the free, single sulfhydryl group of bound C3 by thiol reagents suggested that a functional group other than the -SH acts as a "catalytic" group in this intramolecular hydrolytic reaction. Complete inhibition of the esterase-like activity is observed with stoichiometric amounts of mercuric chloride, palladium chloride, and the bifunctional organic mercurial, 3,6-bis-(acetoxymercuri)-o-toluidine [BAMT]. Since alkyl and aryl mercuric ions do not inhibit the esterase-like activity of C3-[3H]glycerol, it is conjectured that divalent mercury, palladium, and BAMT will form a complex with the -SH group and an atom of the "catalytic" group X having a lone pair of electrons. The structural features of C3 that are essential for the esterase-like activity remain intact after subjecting C3-[3H]glycerol to covalent chromatography on organomercurial agarose. Based on the observed effects of chemical reagents and the kinetic deuterium solvent isotope effect on the esterase-like activity, a general-base mechanism is proposed for the intramolecular hydrolysis of the acyl ester bond in covalently bound C3. The "catalytic" group X is located in the C3d region (residues 317-632 of the alpha chain), since C3d-[3H]glycerol also has esterase-like activity. A general-base mechanism mediated by the same "catalytic" group X may also apply to the formation of acyl ester bonds following the hydrolysis of the internal thiolester bond in native C3.
Mol Immunol 1988 Sep
PMID:The esterase-like activity of covalently bound human third complement protein. 326 82

A large (greater than 250 kb) conjugative plasmid, pMER610, specifying resistance to tellurium and mercury was isolated from an Alcaligenes strain and transferred by conjugation to Escherichia coli AB1157. The acquisition of pMER610 by AB1157 increased the resistance to both telurite and tellurate by 100-fold. Expression of tellurite resistance by pMER610 and the cloned Ter determinant was inducible by prior exposure to tellurite at levels sub-toxic to the sensitive AB1157. Physical analysis of the cloned Ter fragment located the resistance determinant to a 3.55 kb region. Insertion of Tn 1000 (gamma delta) into this region produced two classes of sensitive mutations, fully sensitive and intermediate or hyposensitive, which map in adjacent regions and form two complementation groups. Maxicell analysis identified four polypeptides (15.5, 22, 23 and 41 kDa) expressed by the Ter clone. The 23 kDa polypeptide may not be required for resistance since tellurium-sensitive gamma delta insertion mutations were not detected in the 23 kDa coding region.
Mol Gen Genet 1987 Jun
PMID:Genetic and physical analysis of plasmid genes expressing inducible resistance of tellurite in Escherichia coli. 330 11

An analysis of chromosomal aberrations (structural and numerical) and sister chromatid exchange (SCE) was carried out on 16 people exposed to methylmercury through eating fish caught in Cartagena Bay (Columbia), an area of known methylmercury contamination. Fourteen people whose diet consisted mainly of fish caught in another, noncontaminated area of the Atlantic acted as controls. The results showed a significant difference between the experimental and control groups in methylmercury (MM) concentrations measured in hair and peripheral blood. Subsequently, significant differences between levels of organic mercury in blood and hair were found when all the individuals studied were classified in two groups according to their blood mercury levels. When achromatic lesions were included, the frequency of structural chromosome aberrations differed significantly between the exposed and control groups. Furthermore, a significant correlation (p less than 0.05) was found between structural chromosome aberrations and groups (exposed and control). When achromatic lesions were excluded from the analyses, these differences were not found. There was a significant correlation between SCE and age. This is the first report of a study on the frequency of SCE in a population exposed to methylmercury.
Environ Mol Mutagen 1987
PMID:Genetic effects of methylmercury in human chromosomes: I. A cytogenetic study of people exposed through eating contaminated fish. 367 8

A brief exposure of low dose methylmercuric chloride to monolayer cultures of mouse fetal astrocytes caused a marked shift in the distribution of anionic groups on the surface membrane as evidenced by irregular disruption of cationized ferritin. It is suggested that one of the earliest changes following methyl mercury exposure in embryonic astrocytes includes alterations in the surface charge which may in turn trigger cascading toxic actions of methyl mercury in the developing brain.
Exp Mol Pathol 1986 Apr
PMID:Surface charge alterations in mouse fetal astrocytes due to methyl mercury: an ultrastructural study with cationized ferritin. 369 41


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