THE SEQUENCE OF A SMALL-SUBUNIT OF CYTOCHROME-C-OXIDASE FROM CRITHIDIA-FASCICULATA WHICH IS HOMOLOGOUS TO MAMMALIAN SUBUNIT-IV

The sequence of subunit 8 of cytochrome c oxidase from Crithidia fasci culata was determined by sequencing cDNA and N-terminus of the mature protein (M(r) = 15.7 kDa), The (inferred) protein is homologous to mam malian cox IV and the corresponding cox subunits from yeast, Neurospor a crassa and Dictyostelium discoideum, which is reflected in a very si milar hydropathy profile, Elements that are conserved in the C. fascic ulata sequence include (i) an N-terminal (D/E)-(K/R)-X-K-(X(2))-W-(X(2 ))-(I/L) motif, (ii) a putative membrane-spanning region in the middle portion of the protein, and (iii) a C-terminal W-(X(13))-(N/D)-P moti f. The C. fasciculata protein is synthesized with a cleavable preseque nce.