title: Identification of the carboxyl-terminal amino acids important for the ADP-ribosylation activity of Pseudomonas exotoxin A.
abstract: The ADP-ribosylation domain of Pseudomonas exotoxin A (PE) has been identified to reside in structural domain III (residues 405-613) and a portion of domain Ib (residues 385-404) of the molecule (Hwang, J., FitzGerald, D. J., Adhya, S., and Pastan, I. (1987) Cell 48, 129-136). To further determine the carboxyl end region essential for ADP-ribosylation activity, we constructed sequential deletions at the carboxyl-terminal of PE. Our results show that a clone with a deletion of the carboxyl-terminal amino acid residues from Arg-609 to Lys-613 and replaced with Arg-Asn retained wild-type PE ADP-ribosylation activity. Deletion of the terminal amino acid residues from Ala-596 to Lys-613 and replaced with Val-Ile-Asn reduced ADP-ribosylation activity by 75%, while deletions of 36 or more amino acids from the carboxyl terminus completely lose their ADP-ribosylation activity. These modified PEs were also examined for their ability to block PE cytotoxicity. Our results shown that modified PEs which lost their ADP-ribosylation activity correspondingly lost their cytotoxicity. Furthermore, extracts containing PE fragments without ADP-ribosylation activity were able to block the cytotoxic activity of intact PE. Our results thus indicate that carboxyl-terminal amino acids in the Ser-595 region are crucial for ADP-ribosylation activity and, consequently, cytotoxicity of PE. The modified PEs which have lost their ADP-ribosylation activity may also be a route to new PE vaccines.
authors.affiliation: Institute of Molecular Biology, Academia Sinica, Nankang, Taipei, Republic of China.
authors.forename: J T
authors.initials: JT
authors.lastname: Chow
authors.forename: M S
authors.initials: MS
authors.lastname: Chen
authors.forename: H C
authors.initials: HC
authors.lastname: Wu
authors.forename: J
authors.initials: J
authors.lastname: Hwang
mesh_terms: D036002:ADP Ribose Transferases; D000246:Adenosine Diphosphate Ribose / Q000378:metabolism*; D000595:Amino Acid Sequence; D001427:Bacterial Toxins; D001483:Base Sequence; D003001:Cloning, Molecular; D004262:DNA Restriction Enzymes; D004926:Escherichia coli / Q000235:genetics; D005098:Exotoxins / Q000235:genetics / Q000378:metabolism* / Q000633:toxicity; D015870:Gene Expression; D008969:Molecular Sequence Data; D009154:Mutation; D010446:Peptide Fragments / Q000378:metabolism; D010957:Plasmids; D011550:Pseudomonas aeruginosa; D011994:Recombinant Proteins / Q000235:genetics; D013329:Structure-Activity Relationship; D014169:Transformation, Bacterial; D037521:Virulence Factors; D000097668:Pseudomonas aeruginosa Exotoxin A
chemical_list: D036002:ADP Ribose Transferases; D000246:Adenosine Diphosphate Ribose; D001427:Bacterial Toxins; D004262:DNA Restriction Enzymes; D005098:Exotoxins; D010446:Peptide Fragments; D011994:Recombinant Proteins; D037521:Virulence Factors; D000097668:Pseudomonas aeruginosa Exotoxin A