Isolation and characterization of Trichomonas vaginalis ferredoxin

Abstract

A ferredoxin was purified from the anaerobic protozoon Trichomonas vaginalis. The protein had a molecular weight of 12,000 as assessed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, gel filtration and amino acid analysis. The protein contained seven 1/2-cystine (cystine plus cysteine) residues and one tyrosine, and lacked tryptophan. Chemical analysis and spectral properties of the ferredoxin indicated the presence of a [2Fe-2S] cluster. The complex optical spectrum of the native ferredoxin had peaks at 310 and 450 nm and shoulders near 415 and 550 nm. The molar absorbance of the protein at 450 nm was 8,000 m-1 × cm-1. The EPR spectrum of reduced ferredoxin had two features at g values of 2.02 and 1.94 and revealed axial symmetry. Results of subcellular fractionation studies indicated the ferredoxin to be a major iron-sulfur protein of the cells and to be located in the hydrogenosome. The ability of the ferredoxin to function as an electron carrier was demonstrated by its reduction by pyruvate: ferredoxin oxidoreductase and hydrogenase as detected by EPR spectroscopy and by its stimulation of metronidazole reduction by these enzymes. These observations implicate ferredoxin as an important electron transport component in hydrogenosomes of T. vaginalis. © 1984 Carlsberg Laboratory.