| Literature References | 1. FREEMONT P.S.
The RING finger. A novel protein sequence motif related to the zinc finger.
ANN.N.Y.ACAD.SCI. 684 174-192 (1993).
2. BORDEN, K.L.B. AND FREEMONT, P.S.
The RING finger domain: a recent example of a sequence-structure family.
CURR.OPIN.STRUCT.BIOL. 6 395-401 (1996).
3.SAURIN, A.J., BORDEN, K.L., BODDY, M.N. AND FREEMONT, P.S.
Does this have a familiar RING?
TRENDS BIOCHEM.SCI. 21(6) 208-214 (1996).
4. BORDEN, K.L.
RING fingers and B-boxes: zinc-binding protein-protein interaction domains.
BIOCHEM.CELL BIOL. 76 351-358 (1998).
5. BORDEN, K.L., LALLY, J.M., MARTIN, S.R., O'REILLY, N.J., ETKIN, L.D.
AND FREEMONT, P.S.
Novel topology of a zinc-binding domain from a protein involved in
regulating early Xenopus development.
EMBO J. 14(23) 5947-5956 (1995).
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| Documentation | A number of eukaryotic and viral proteins contain a conserved 40-60 residue
cysteine-rich domain, variously termed a C3HC4 zinc-finger or `RING' finger
[1-3]. The finger binds two atoms of zinc, and is probably involved in
mediating protein-protein interactions. The 3D structure [2,3] of the zinc
ligation system is unique to the RING domain and is referred to as the
"cross-brace" motif, illustrated schematically below:
x x x x x x
x x x x
x x x
x x x x
C C C C
x \ / x x \ / x
x Zn x x Zn x
C / \ C H / \ C
x x x x
x x x x x x x x x x x x x
Several proteins that contain RING fingers also contain a well-conserved
40-residue cysteine-rich domain termed a B-box zinc finger. Often, one or
two copies of the B-box are associated with a coiled coil domain in addition
to the ring finger, forming a tripartite motif. The tripartite motif is
found in transcription factors, ribonucleoproteins and proto-oncoproteins,
but no function has yet been ascribed to the domain [4].
The solution structure of the B-box motif has been determined by NMR [5].
The protein is a monomer, with 2 beta-strands, 2 helical turns and 3
extended loop regions packed in a novel topology [5]. Of 7 potential zinc
ligands, only 4 are used, binding a single zinc atom in a C2-H2 tetrahedral
arrangement [5]. The B-box structure differs in tertiary fold from all
other known zinc-binding motifs.
BBOXZNFINGER is a 2-element fingerprint that provides a signature for
B-box zinc finger proteins. The fingerprint was derived from an initial
alignment of 7 sequences: the motifs were drawn from conserved regions
spanning the full length of the finger domain. Five iterations on SPTR37_10f
were required to reach convergence, at which point a true set comprising 33
sequences was identified.
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