Respiratory Pigments of Crithidia fasciculata

Abstract

Mitochondria were isolated from the heme-requiring insect trypanosomatid, Crithidia fasciculata , which had respiratory activity, showed a P/O ratio with succinate of 0.5 to 1.0, and contained 40 to 50% of the heme a and heme c found in the intact cells. Cytochromes b, c 555 , possibly c 1 , cytochrome oxidase, a carbon monoxide-binding pigment, and flavoproteins were detectable in the spectra of both intact cells and mitochondria. Cytochrome c 555 is a basic protein that was extracted from cells and mitochondria with salt solutions. The molar ratio of heme c to heme a was approximately 2:1 in both cells and mitochondria. This organism could possibly serve as a model for studies of the respiratory activity of the pathogenic trypanosomes.