The sequence of a small subunit of cytochrome c oxidase from Crithidia fasciculata which is homologous to mammalian subunit IV

Abstract

The sequence of subunit 8 of cytochrome c oxidase from Crithidia fasciculata was determined by sequencing cDNA and N-terminus of the mature protein (M(r) = 15.7 kDa). The (inferred) protein is homologous to mammalian cox IV and the corresponding cox subunits from yeast, Neurospora crassa and Dictyostelium discoideum, which is reflected in a very similar hydropathy profile. Elements that are conserved in the C. fasciculata sequence include (i) an N-terminal (D/E)-(K/R)-X-K-(X2)-W-(X2)-(I/L) motif, (ii) a putative membrane-spanning region in the middle portion of the protein, and (iii) a C-terminal W-(X13)-(N/D)-P motif. The C. fasciculata protein is synthesized with a cleavable presequence.