PURIFICATION AND CHARACTERIZATION OF FERRITIN FROM CAMPYLOBACTER-JEJUNI

We purified an iron-containing protein from Campylobacter jejuni using ultracentrifugation and ion-exchange chromatography. Electron microsc opy of this protein revealed circular particles with a diameter of 11. 5 nm and a central core with a diameter of 5.5 nm. The protein was com posed of a single peptide of 21 kDa and did not serologically cross-re act with horse spleen ferritin. The UV-visible spectrum of the protein showed no absorption peaks in the visible region, indicating that lit tle or no heme is bound. The ratio of Fe:phosphate of C. jejuni ferrit in was 1.5:1. From these morphological and chemical examinations, we c oncluded that the C. jejuni purified protein is a ferritin of the same class as that of Helicobacter pylori and Bacteroides fragilis and dif fers from the heme-containing bacterioferritin of Escherichia coli. Th e 30 N-terminal amino acids were sequenced and were found to resemble the sequences of other ferritins strongly (H. pylori ferritin, 73% ide ntity; B. fragilis ferritin, 50% identity; E. coli gene-165 product, 5 0% identity), and to a lesser degree, bacterioferritins (E. coli bacte rioferritin, 26% identity; Azotobacter vinelandii, 26% identity; horse spleen ferritin 30% identity). Proteins that cross-reacted with antis erum against the ferritin of C. jejuni were found in other Campylobact er species and in H. pylori, but not in Vibrio, E. coli, or Pseudomona s aeruginosa.