PUL ID

PUL0111

PubMed

9642246, J Biol Chem. 1998 Jul 3;273(27):16860-4. doi: 10.1074/jbc.273.27.16860.

Characterization method

enzyme activity assay, Northern Blot, transport assay

Genomic accession number

U00096.3

Nucelotide position range

4340720-4344790

Substrate

melibiose

Loci

melRAB

Species

Escherichia coli/562

Degradation or Biosynthesis

degradation

Gene Name

Locus Tag

Protein ID

Gene Position

GenBank Contig Range

EC Number

melR b4118 AAC77079.1 0 - 909 (-) U00096.3:4340720-4341629 -
melA b4119 AAC77080.1 1191 - 2547 (+) U00096.3:4341911-4343267 3.2.1.22
melB b4120 AAC77081.2 2649 - 4071 (+) U00096.3:4343369-4344791 -

Cluster number

1

Gene name

Gene position

Gene type

Found by CGCFinder?

melR 1 - 909 (-) TF: DBD-Pfam|HTH_AraC,DBD-Pfam|HTH_AraC,DBD-SUPERFAMILY|0043644,DBD-SUPERFAMILY|0035607,DBD-SUPERFAMILY|0035607 No
melA 1192 - 2547 (+) CAZyme: GH4 Yes
melB 2650 - 4071 (+) TC: gnl|TC-DB|A7ZUZ0|2.A.2.1.1 Yes

PUL ID

PUL0111

PubMed

9642246, J Biol Chem. 1998 Jul 3;273(27):16860-4. doi: 10.1074/jbc.273.27.16860.

Title

Conversion of temperature-sensitive to -resistant gene expression due to mutations in the promoter region of the melibiose operon in Escherichia coli.

Author

Tamai E, Shimamoto T, Tsuda M, Mizushima T, Tsuchiya T

Abstract

The melibiose utilization system of Escherichia coli W3133, a derivative of K12, is nonfunctional between 37 and 42 degreesC. The reason for this temperature sensitivity was thought to be that the melibiose transporter (MelB) of W3133 cells was temperature-sensitive. A mutant W3133-2 has been isolated as a temperature-resistant strain that can utilize melibiose between 37 and 42 degreesC. However, we found that the melibiose transporter of the W3133-2 was still temperature-sensitive. Half-life activities of the melibiose transporter at 37 degreesC (or 40 degreesC) in both E. coli W3133 and W3133-2 were exactly the same. Furthermore, we found that the nucleotide sequence of coding region of the melB structural gene (the second gene of the melibiose operon) of W3133-2 was exactly the same as that of W3133. Activity of alpha-galactosidase (product of the first gene, melA, of the melibiose operon) of W3133 cells grown at 40 degreesC was very low, although that of W3133-2 cells grown at 40 degreesC was high. These observations suggested that expression of the melibiose operon in W3133 is also temperature-sensitive. In fact, we found that the expression in W3133 cells was temperature-sensitive, while that in W3133-2 cells was temperature-resistant, by analyzing mRNA levels using the Northern blot method. Furthermore, we identified mutations in the promoter region of the melibiose operon of W3133-2 that resulted in the elongation of an 18 nucleotide inverted repeat sequence to a 28-nucleotide repeat sequence present immediately upstream of the -35 region. This may stabilize a possible stem structure due to the inverted repeat at 37-42 degreesC.