Structure-function analysis of the Z-DNA-binding domain Zalpha of dsRNA adenosine deaminase type I reveals similarity to the (alpha + beta) family of helix-turn-helix proteins.
RNA editing alters pre-mRNA through site-selective adenosine deamination, which results in codon changes that lead to the production of novel proteins. An enzyme that catalyzes this reaction, double-stranded RNA adenosine deaminase (ADAR1), contains two N-terminal Z-DNA-binding motifs, Zalpha and Zbeta, the function of which is as yet unknown. In this study, multidimensional NMR spectroscopy was used to show that the topology of Zalpha is alpha1beta1alpha2alpha3beta2beta3. Long-range NOEs indicate that beta1 and beta3 interact with each other. Site-directed mutagenesis was used to identify residues in alpha3, beta3 and the loop connecting beta2 to beta3 that affect Z-DNA binding. Also identified were 11 hydrophobic residues that are essential for protein stability. Comparison with known structures reveals some similarity between Zalpha and (alpha + beta) helix-turn-helix proteins, such as histone 5 and the family of hepatocyte nuclear factor-3 winged-helix-turn-helix transcription factors. Taken together, the structural and functional data suggest that recognition of Z-DNA by Zalpha involves residues in both the alpha3 helix and the C-terminal beta-sheet.
Schade
M
M
Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
Turner
C J
CJ
Lowenhaupt
K
K
Rich
A
A
Herbert
A
A
D000243:Adenosine Deaminase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D001665:Binding Sites / Q000235:genetics; D002942:Circular Dichroism; D004247:DNA / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics; D019077:Helix-Turn-Helix Motifs; D006801:Humans; D066298:In Vitro Techniques; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D016601:RNA-Binding Proteins; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism
D016601:RNA-Binding Proteins; D011993:Recombinant Fusion Proteins; D004247:DNA; C567955:ADARB1 protein, human; D000243:Adenosine Deaminase