title: Localization of a region of the S1 subunit of pertussis toxin required for efficient ADP-ribosyltransferase activity.
abstract: Purified recombinant S1 subunit of pertussis toxin (rS1) possessed similar NAD glycohydrolase and ADP-ribosyltransferase activities as S1 subunit purified from pertussis toxin. Purified rS1 and C180 peptide, a deletion peptide which contains amino acids 1-180 of rS1, had Km values for NAD of 24 and 13 microM and kcat values of 22 and 24 h-1, respectively, in the NAD glycohydrolase reaction. In contrast, under linear velocity conditions, the C180 peptide possessed less than 1% of the ADP-ribosyltransferase activity of rS1 using transducin as target. Radiolabeled tryptic peptides of transducin that had been ADP-ribosylated by either rS1 or C180 peptide were identical which suggested that both rS1 and C180 peptide ADP-ribosylated the same amino acid within transducin. To extend the functional primary amino acid map of the S1 subunit, two carboxyl-terminal deletions were constructed. One deletion, C195, removed the 40 carboxyl-terminal amino acids and the other, C219, removed the 16 carboxyl-terminal amino acids of the S1 subunit. Both C195 and C219 migrated in reduced sodium dodecyl sulfate-polyacrylamide gel electrophoresis with apparent molecular masses of 22,000 and 27,500 Da, respectively. Relative to the C180 peptide C195 possessed 10-20-fold increase and C219 possessed 100-150-fold increase in ADP-ribosyltransferase activities. In addition, C219 appeared to have the same ADP-ribosyltransferase activity as rS1. These studies indicate that (i) rS1, purified from Escherichia coli, possesses biochemical properties similar to S1 subunit purified from pertussis toxin, (ii) amino acids 1-180 of the S1 subunit contain residues required for NAD binding, N-glycosidic cleavage, and transfer of ADP-ribose to transducin, and (iii) residues between 181 and 219 of the S1 subunit are required for efficient ADP-ribosyltransferase activity.
authors.affiliation: Department of Microbiology, Medical College of Wisconsin, Milwaukee 53226.
authors.forename: G
authors.initials: G
authors.lastname: Cortina
authors.forename: J T
authors.initials: JT
authors.lastname: Barbieri
mesh_terms: D000246:Adenosine Diphosphate Ribose / Q000378:metabolism*; D002384:Catalysis; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli / Q000235:genetics; D015964:Gene Expression Regulation, Bacterial; D009876:Operon; D037342:Pertussis Toxin; D010957:Plasmids; D015293:Transducin / Q000235:genetics / Q000378:metabolism; D014357:Trypsin; D010566:Virulence Factors, Bordetella / Q000235:genetics*
chemical_list: D010566:Virulence Factors, Bordetella; D000246:Adenosine Diphosphate Ribose; D037342:Pertussis Toxin; D014357:Trypsin; D015293:Transducin