title: A class of zinc fingers involved in protein-protein interactions biophysical characterization of CCHC fingers from fog and U-shaped.
abstract: Zinc fingers (ZnFs) are extremely common protein domains. Several classes of ZnFs are distinguished by the nature and spacing of their zinc-coordinating residues. While the structure and function of some ZnFs are well characterized, many others have been identified only through their amino acid sequence. A number of proteins contain a conserved C-X2-C-X12-H-X1-5-C sequence, which is similar to the spacing observed for the 'classic' CCHH ZnFs. Although these domains have been implicated in protein-protein (and not protein-nucleic acid) interactions, nothing is known about their structure or function at a molecular level. Here, we address this problem through the expression and biophysical characterization of several CCHC-type zinc fingers from the erythroid transcription factor FOG and the related Drosophila protein U-shaped. Each of these domains does indeed fold in a zinc-dependent fashion, coordinating the metal in a tetrahedral manner through the sidechains of one histidine and three cysteine residues, and forming extremely thermostable structures. Analysis of CD spectra suggests an overall fold similar to that of the CCHH fingers, and indeed a point mutant of FOG-F1 in which the final cysteine residue is replaced by histidine remains capable of folding. However, the CCHC (as opposed to CCHH) motif is a prerequisite for GATA-1 binding activity, demonstrating that CCHC and CCHH topologies are not interchangeable. This demonstration that members of a structurally distinct subclass of genuine zinc finger domains are involved in the mediation of protein-protein interactions has implications for the prediction of protein function from nucleotide sequences.
authors.affiliation: Department of Biochemistry, University of Sydney, NSW, Australia.
authors.forename: J M
authors.initials: JM
authors.lastname: Matthews
authors.forename: K
authors.initials: K
authors.lastname: Kowalski
authors.forename: C K
authors.initials: CK
authors.lastname: Liew
authors.forename: B K
authors.initials: BK
authors.lastname: Sharpe
authors.forename: A H
authors.initials: AH
authors.lastname: Fox
authors.forename: M
authors.initials: M
authors.lastname: Crossley
authors.forename: J P
authors.initials: JP
authors.lastname: MacKay
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002352:Carrier Proteins / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D003545:Cysteine / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D029721:Drosophila Proteins; D004331:Drosophila melanogaster; D050981:Erythroid-Specific DNA-Binding Factors; D006639:Histidine / Q000235:genetics / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D019476:Insect Proteins / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D009687:Nuclear Proteins / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D011485:Protein Binding; D017510:Protein Folding; D017433:Protein Structure, Secondary; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D013057:Spectrum Analysis; D013696:Temperature; D013816:Thermodynamics; D014157:Transcription Factors / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D020798:Two-Hybrid System Techniques; D015032:Zinc / Q000378:metabolism; D016335:Zinc Fingers / Q000235:genetics / Q000502:physiology*
chemical_list: D002352:Carrier Proteins; D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D050981:Erythroid-Specific DNA-Binding Factors; D019476:Insect Proteins; D009687:Nuclear Proteins; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors; C109258:ush protein, Drosophila; D006639:Histidine; D015032:Zinc; D003545:Cysteine