Tn5044-conferred mercury resistance depends on temperature: the complexity of the character of thermosensitivity.
Escherichia coli K12 containing the transposon Tn5044 mer operon (merR, T, P, C, and A genes) is resistant to mercuric chloride at 30 degrees C but sensitive to this compound at 37-41.5 degrees C. We have studied the mechanism underlying the temperature-sensitive nature of this mercury resistance phenotype, and found that the expression of the Tn5044 merA gene coding for mercuric reductase (MerA) is severely inhibited at non-permissive temperatures. Additionally, MerA showed a considerably reduced functional activity in vivo at non-permissive temperatures. However, the temperature-sensitive character of the functioning of this enzyme in cell extracts, where it interacted with one of the low-molecular weight SH compounds rather than with the transport protein MerT (as is the case in vivo), was not apparent. These data suggest that the temperature-sensitive mercury resistance phenotype should stay under control at two stages: when the merA gene is expressed and when its product interacts with MerT to accept the mercuric ion.
Kholodii
Gennady
G
Institute of Molecular Genetics, Russian Academy of Sciences, Moscow. kholodii@img.ras.ru
Bogdanova
Elena
E
D000595:Amino Acid Sequence; D003001:Cloning, Molecular; D004251:DNA Transposable Elements; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics* / Q000254:growth & development; D005798:Genes, Bacterial; D005822:Genetic Vectors; D008628:Mercury / Q000494:pharmacology*; D008969:Molecular Sequence Data; D016415:Sequence Alignment; D013696:Temperature
D004251:DNA Transposable Elements; D008628:Mercury