title: Novel topology of a zinc-binding domain from a protein involved in regulating early Xenopus development.
abstract: Xenopus nuclear factor XNF7, a maternally expressed protein, functions in patterning of the embryo. XNF7 contains a number of defined protein domains implicated in the regulation of some developmental processes. Among these is a tripartite motif comprising a zinc-binding RING finger and B-box domain next to a predicted alpha-helical coiled-coil domain. Interestingly, this motif is found in a variety of protein including several proto-oncoproteins. Here we describe the solution structure of the XNF7 B-box zinc-binding domain determined at physiological pH by 1H NMR methods. The B-box structure represents the first three-dimensional structure of this new motif and comprises a monomer have two beta-strands, two helical turns and three extended loop regions packed in a novel topology. The r.m.s. deviation for the best 18 structures is 1.15 A for backbone atoms and 1.94 A for all atoms. Structure calculations and biochemical data shows one zinc atom ligated in a Cys2-His2 tetrahedral arrangement. We have used mutant peptides to determine the metal ligation scheme which surprisingly shows that not all of the seven conserved cysteines/histidines in the B-box motif are involved in metal ligation. The B-box structure is not similar in tertiary fold to any other known zinc-binding motif.
authors.affiliation: Laboratory of Molecular Structure, National Institute for Medical Research, London, UK.
authors.forename: K L
authors.initials: KL
authors.lastname: Borden
authors.forename: J M
authors.initials: JM
authors.lastname: Lally
authors.forename: S R
authors.initials: SR
authors.lastname: Martin
authors.forename: N J
authors.initials: NJ
authors.lastname: O'Reilly
authors.forename: L D
authors.initials: LD
authors.lastname: Etkin
authors.forename: P S
authors.initials: PS
authors.lastname: Freemont
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D003196:Computer Graphics; D004268:DNA-Binding Proteins; D004527:Egg Proteins; D006860:Hydrogen Bonding; D007501:Iron / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000737:chemistry*; D010455:Peptides / Q000737:chemistry; D010750:Phosphoproteins / Q000737:chemistry*; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D016415:Sequence Alignment; D014981:Xenopus / Q000196:embryology; D029867:Xenopus Proteins; D015032:Zinc / Q000378:metabolism*; D016335:Zinc Fingers
chemical_list: D004268:DNA-Binding Proteins; D004527:Egg Proteins; D009687:Nuclear Proteins; D010455:Peptides; D010750:Phosphoproteins; D029867:Xenopus Proteins; C071551:XNF7 protein, Xenopus; D007501:Iron; D015032:Zinc