The amino acid sequence of the β-subunit: Of porcine enterotoxigenic Escherichia coli enterotoxin — Analysis and comparison with literature data

The pathogenesis of diarrhoeal disease due to human enterotoxigenic Escherichia coli absolutely requires the expression of fimbriae. The expression of CS1 fimbriae is positively regulated by the AraC-like protein Rns. AraC-like proteins are DNA-binding proteins that typically contain two helix–turn–helix (HTH) motifs. A program of pentapeptide insertion mutagenesis of the Rns protein was performed, and this revealed that both HTH motifs are required by Rns to positively regulate CS1 fimbrial gene expression. Intriguingly, a pentapeptide insertion after amino acid C102 reduced the ability of Rns to transactivate CS1 fimbrial expression. The structure of Rns in this vicinity (NACRS) was predicted to be disordered and thus might act as a flexible linker. This hypothesis was confirmed by deletion of this amino acid sequence from the Rns protein; a truncated protein that lacked this sequence was no longer functional. Strikingly, this sequence could be functionally substituted in vivo and in vitro by a flexible seven amino acid sequence from another E. coli AraC-like protein RhaS. Our data indicate that HTH motifs and a flexible sequence are required by Rns for maximal activation of fimbrial gene expression.

Download Full-text

A unique amino acid sequence of the B subunit of a heat-labile enterotoxin isolated from a human enterotoxigenic Escherichia coli

Microbial Pathogenesis ◽

10.1016/0882-4010(87)90079-9 ◽

1987 ◽

Vol 2 (5) ◽

pp. 381-390 ◽

Cited By ~ 20

Author(s):

Takao Tsuji ◽

Tetsuya Iida ◽

Takeshi Honda ◽

Toshio Miwatani ◽

Masahiro Nagahama ◽

...

Keyword(s):

Escherichia Coli ◽

Amino Acid ◽

Amino Acid Sequence ◽

Enterotoxigenic Escherichia Coli ◽

B Subunit ◽

Heat Labile ◽

Unique Amino Acid Sequence ◽

Unique Amino Acid

Download Full-text

Different Rifampin Sensitivities of Escherichia coli and Mycobacterium tuberculosis RNA Polymerases Are Not Explained by the Difference in the β-Subunit Rifampin Regions I and II

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.49.4.1587-1590.2005 ◽

2005 ◽

Vol 49 (4) ◽

pp. 1587-1590 ◽

Cited By ~ 12

Author(s):

N. Zenkin ◽

A. Kulbachinskiy ◽

I. Bass ◽

V. Nikiforov

Keyword(s):

Escherichia Coli ◽

Amino Acids ◽

Mycobacterium Tuberculosis ◽

Amino Acid ◽

Amino Acid Sequence ◽

Rna Polymerase ◽

Β Subunit ◽

E Coli ◽

Increased Sensitivity ◽

The Difference

ABSTRACT Mycobacterium tuberculosis RNA polymerase is 1,000-fold more sensitive to rifampin than Escherichia coli RNA polymerase. Chimeric E. coli RNA polymerase in which the β-subunit segment encompassing rifampin regions I and II (amino acids [aa] 463 through 590) was replaced with the corresponding region from M. tuberculosis (aa 382 through 509) did not show an increased sensitivity to the antibiotic. Thus, the difference in amino acid sequence between the rifampin regions I and II of the two species does not account for the difference in rifampin sensitivity of the two polymerases.

Download Full-text