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* Rieske iron-sulfur protein signatures *
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Ubiquinol-cytochrome c reductase (EC 1.10.2.2)  (also known as the bc1 complex
or complex III) is  one of the  electron transport  chains of mitochondria and
of some aerobic prokaryotes; it catalyzes the  oxidoreduction of ubiquinol and
cytochrome c. In the chloroplast of plants and in cyanobacteria plastoquinone-
plastocyanin  reductase (EC 1.10.99.1)  (also  known as  the b6f  complex)  is
functionally  similar  and catalyzes  the  oxidoreduction of plastoquinol  and
cytochrome f.

One of the components  of  these  electron  transfer systems is an iron-sulfur
protein with a 2Fe-2S cluster,  which is  called the Rieske protein [1,2]. The
Rieske protein contains approximately 190 amino acid residues. The iron-sulfur
cluster is complexed to the protein through cysteine and histidine residues.

It is not known  with  certitude  which  cysteine  and histidine  residues are
involved in binding the iron-sulfur cluster.   However there are two perfectly
conserved regions in Rieske proteins, which  each contain two cysteines and an
histidine.  It has  been  proposed that the two cysteines in the first region,
and the first cysteine and the  histidine of  the second region are the 2Fe-2S
ligands. We have selected the two conserved regions as signature patterns.

-Consensus pattern: C-T-H-L-G-C-[LIV]
                    [The two C's may be 2Fe-2S ligands]
-Sequences known to belong to this class detected by the pattern: ALL.
-Other sequence(s) detected in SWISS-PROT: NONE.

-Consensus pattern: C-P-C-H-G-S
                    [The first C and the H may be 2Fe-2S ligands]
-Sequences known to belong to this class detected by the pattern: ALL.
-Other sequence(s) detected in SWISS-PROT: NONE.

-Last update: December 1991 / Patterns and text revised.

[ 1] Gatti F.L., Meinhardt S.W., Ohnishi T., Tzagoloff A.
     J. Mol. Biol. 205:421-435(1989).
[ 2] Kallas T., Spiller S., Malkin R.
     Proc. Natl. Acad. Sci. U.S.A. 85:5794-5798(1988).