Autoprocessing of the Escherichia coli AIDA-I autotransporter: a new mechanism involving acidic residues in the junction region.
The cleavage of the autotransporter adhesin involved in diffuse adherence (AIDA-I) of Escherichia coli yields a membrane-embedded fragment, AIDAc, and an extracellular fragment, the mature AIDA-I adhesin. The latter remains noncovalently associated with AIDAc but can be released by heat treatment. In this study we determined the mechanism of AIDA-I cleavage. We showed that AIDA-I processing is an autocatalytic event by monitoring the in vitro cleavage of an uncleaved mutant protein isolated from inclusion bodies. Furthermore, by following changes in circular dichroism spectra and protease resistance of the renaturated protein, we showed that the cleavage of the protein is correlated with folding. With site-directed deletions, we showed that the catalytic activity of the protein lies in a region encompassing amino acids between Ala-667 and Thr-953, which includes the conserved junction domain of some autotransporters. With site-directed point mutations, we also found that Asp-878 and Glu-897 are involved in the processing of AIDA-I and that a mutation preserving the acidic side chain of Asp-878 was tolerated, giving evidence that this carboxylic acid group is directly involved in catalysis. Last, we confirmed that cleavage of AIDA-I is intramolecular. Our results unveil a new mechanism of auto-processing in the autotransporter family.
Charbonneau
Marie-Ève
MÈ
From the Canada Research Chair on Bacterial Animal Diseases, Université de Montréal, Faculté de Médecine Vétérinaire, 3200 Sicotte, St.-Hyacinthe, Québec J2S 7C6, Canada.
Janvore
Julie
J
From the Canada Research Chair on Bacterial Animal Diseases, Université de Montréal, Faculté de Médecine Vétérinaire, 3200 Sicotte, St.-Hyacinthe, Québec J2S 7C6, Canada.
Mourez
Michael
M
From the Canada Research Chair on Bacterial Animal Diseases, Université de Montréal, Faculté de Médecine Vétérinaire, 3200 Sicotte, St.-Hyacinthe, Québec J2S 7C6, Canada. Electronic address: m.mourez@umontreal.ca.
D018830:Adhesins, Escherichia coli / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics; D017931:DNA Primers / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010446:Peptide Fragments / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011487:Protein Conformation; D017510:Protein Folding; D011499:Protein Processing, Post-Translational; D017433:Protein Structure, Secondary; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid
C075559:AIDA-I protein, E coli; D018830:Adhesins, Escherichia coli; D017931:DNA Primers; D010446:Peptide Fragments; D011994:Recombinant Proteins