IDENTIFICATION OF A NEUTROPHIL CHEMOTACTIC FACTOR FROM TRITRICHOMONAS-FETUS AS SUPEROXIDE-DISMUTASE

Antibodies to a neutrophil chemotactic factor from Tritrichomonas foet us were used to screen a T. foetus cDNA expression library in lambda g t11. All positive clones were identified as homologs of iron-containin g superoxide dismutase (SOD). Native gel electrophoresis showed that t he antibodies indeed recognized T. foetus antigens with SOD activity. Two SOD genes were found in T. foetus, and cloned and sequenced as par ts of larger genomic segments of 3844 and 4089 base pairs. Transcripti on initiated between the first and second methionine codons of each ge nomic open reading frame, generating mRNAs with 5' untranslated region s of 11-15 bases, and encoding proteins of 195 amino acids. The two SO D coding sequences lacked obvious introns. They were 79% identical at both the nucleotide and amino acid levels. Both SOD genes were inserte d into a eukaryotic expression vector and stably expressed in mammalia n cells; both proteins were recognized by the antibodies, and both ass umed a cytosolic, extranuclear distribution in these cells. Histidine- tagged forms of both T. foetus SODs were expressed in E. coli and afte r purification, found to have neutrophil chemotactic activity similar to the non-recombinant factor purified from T. foetus. Identification of this neutrophil chemotactic factor as SOD provides additional insig ht into the host-parasite interaction. (C) 1997 Elsevier Science B.V.