IDENTIFICATION, CDNA SEQUENCE AND DEDUCED AMINO-ACID-SEQUENCE OF THE MITOCHONDRIAL RIESKE IRON-SULFUR PROTEIN FROM THE GREEN-ALGA CHLAMYDOMONAS-REINHARDTII - IMPLICATIONS FOR PROTEIN TARGETING AND SUBUNIT INTERACTION

Specific oligonucleotide probes were used to isolate a cDNA clone for the mitochondrial Rieske iron-sulfur protein of the green alga Chlamyd omonas reinhardtii. The protein is synthesized as a longer precursor w ith a cleavable N-terminal presequence of 54 amino acids but without a C-terminal extension. Comparison of the predicted secondary structure of this N-terminal sequence with that of the targeting signal of the chloroplast Rieske protein from C. reinhardtii [de Vitry (1994) J. Bio l. Chem. 269, 7603-7609] indicates that, although they both have the p otential to form amphiphilic a helices, the mitochondrial presequence may form a more hydrophobic helix that could penetrate deeper into the membrane. The N-terminal part of the mature mitochondrial Rieske prot ein is characterized by a long, strongly hydrophilic N-terminal domain and by a positive charge in the middle of the hydrophobic stretch tha t is presumed to interact with the be, complex. Thus, the protein from C. reinhardtii differs from the Rieske proteins from mammals or fungi .