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* Zinc finger, C2H2 type, domain *
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'Zinc finger' domains [1-5]  are nucleic acid-binding protein structures first
identified in  the Xenopus  transcription  factor TFIIIA.   These domains have
since been found  in  numerous nucleic acid-binding proteins.   A zinc  finger
domain is composed of 25 to 30 amino-acid residues.  There are two cysteine or
histidine residues  at  both extremities of the domain,  which are involved in
the tetrahedral coordination of a zinc atom. It has been proposed that such  a
domain interacts  with about five nucleotides. A schematic representation of a
zinc finger domain is shown below:

                                 x  x
                               x      x
                              x        x
                              x        x
                              x        x
                              x        x
                               C      H
                             x   \  /   x
                            x     Zn     x
                             x  /    \  x
                               C      H
                      x x x x x        x x x x x

Many classes  of  zinc  fingers  are characterized according to the number and
positions of  the  histidine  and  cysteine residues involved in the zinc atom
coordination.  In the  first class to be characterized, called C2H2, the first
pair of zinc coordinating  residues  are cysteines, while the  second pair are
histidines. A  number  of  experimental  reports  have  demonstrated the zinc-
dependent DNA or RNA binding property of some members of this class.

Some of the proteins known to include C2H2-type zinc fingers are listed below.
We have indicated, between brackets, the number of zinc  finger regions  found
in each  of these proteins; a '+' symbol indicates that only partial  sequence
data is available and that additional finger domains may be present.

 - Saccharomyces cerevisiae: ACE2 (3), ADR1 (2), FZF1 (5), MIG1 (2), MSN2 (2),
   MSN4 (2),  RGM1  (2),  RIM1 (3), RME1 (3), SFP1 (2), SSL1 (1), STP1 (3) and
   SWI5 (3).
 - Emericella nidulans: brlA (2), creA (2).
 - Drosophila: Cf2 (7),  ci-D (5), Disconnected (2),  Escargot (5), Glass (5),
   Hunchback (6), Kruppel (5),  Kruppel-H (4+),   Odd-skipped (4),  Snail (5),
   Serependity locus beta (6),  delta (7),  h-1 (8),  Suppressor of hairy wing
   su(Hw) (12),   Suppressor  of variegation suvar(3)7 (5),  Teashirt (3)  and
   Tramtrack (2).
 - Xenopus: transcription factor TFIIIA (9),  p43  from RNP particle (9), Xfin
   (37 !!), Xsna (5),  gastrula XlcGF5.1 to XlcGF71.1 (from 4+ to 11+), Oocyte
   XlcOF2 to XlcOF22 (from 7 to 12).
 - Mammalian:  basonuclin  (6),  transcription factor Sp1 (3), transcriptional
   repressor YY1  (4),  Wilms' tumor protein (4), EGR1/Krox24 (3), EGR2/Krox20
   (3), Evi-1 (10), GLI1 (5), GLI2 (4+), GLI3 (3+), HIV-EP1/ZNF40 (4), HIV-EP2
   (2), KR1 (9+), KR2 (9),  KR3 (15+), KR4 (14+), KR5 (11+), HF.12 (6+), REX-1
   (4), ZfX (13),  ZfY (13), Zfp-35 (18), ZNF35 (10), ZNF42/MZF-1 (13),  ZNF43
   (22), ZNF46/Kup (2), ZNF76 (7), ZNF91 (36), ZNF133 (3).

In addition to the conserved zinc ligand residues it has been shown [6] that a
number of other positions are  also  important for the structural integrity of
the C2H2 zinc fingers. The  best  conserved  position is  found  four residues
after the second cysteine; it is generally an aromatic or aliphatic residue.

-Consensus pattern: C-x(2,4)-C-x(3)-[LIVMFYWC]-x(8)-H-x(3,5)-H
                    [The two C's and two H's are zinc ligands]
-Sequences known to belong to this class detected by the pattern: ALL.
-Other sequence(s) detected in SWISS-PROT: 20.

-Note: in  proteins  that  include many copies of the C2H2 zinc finger domain,
 incomplete or  degenerate  copies  of  the  domain  are frequently found. The
 former are generally found at the extremity of the zinc finger region(s); the
 latter have  typically  lost one or more of the zinc-coordinating residues or
 are interrupted  by  insertions or deletions. Our pattern does not detect any
 of these finger domains.

-Last update: June 1994 / Pattern and text revised.

[ 1] Klug A., Rhodes D.
     Trends Biochem. Sci. 12:464-469(1987).
[ 2] Evans R.M., Hollenberg S.M.
     Cell 52:1-3(1988).
[ 3] Payre F., Vincent A.
     FEBS Lett. 234:245-250(1988).
[ 4] Miller J., Mc Lachlan A.D., Klug A.
     EMBO J. 4:1609-1614(1985).
[ 5] Berg J.M.
     Proc. Natl. Acad. Sci. U.S.A. 85:99-102(1988).
[ 6] Rosenfeld R., Margalit H.
     J. Biomol. Struct. Dyn. 11:557-570(1993).