Histidine-44 of the A subunit of Escherichia coli enterotoxin is involved in its enzymatic and biological activities

Michio Kato, Seiji Imamura, Hidetsugu Kawase, Akio Miyama, Takao Tsuji

Research output: Contribution to journalArticlepeer-review

8 Citations (Scopus)

Abstract

We examined the role in toxicity of histidine-44 of the A subunit of Escherichia coli enterotoxin which is located in the active site cavity close to glutamic acid-112. Although amino acid substitution of histidine-44 usually renders a mutant toxin unstable to trypsin, one mutant, alanine-44 (His44Ala) was found to be stable. His44Ala did not show any agmatine:ADP- ribosyltransferase activity in the presence or absence of recombinant ADP- ribosylation factor. It showed no diarrheal or rabbit skin permeability activity and was a competitor in enterotoxin-ADP-ribosyltransferase assays containing recombinant ADP-ribosylation factor. These results suggest that like glutamic acid-112, histidine-44 plays an essential role in toxicity. A tentative model, which explains NAD+ catalysis and the transfer of the ADP- ribosyl moiety to a target amino acid, is proposed for histidine-44 and glutamic acid-112.

Original languageEnglish
Pages (from-to)219-225
Number of pages7
JournalFEMS Microbiology Letters
Volume152
Issue number2
DOIs
Publication statusPublished - 15-07-1997

All Science Journal Classification (ASJC) codes

  • Microbiology
  • Molecular Biology
  • Genetics

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