A novel zinc-binding motif revealed by solution structures of DNA-binding domains of Arabidopsis SBP-family transcription factors.
SQUAMOSA promoter binding proteins (SBPs) form a major family of plant-specific transcription factors related to flower development. Although SBPs are heterogeneous in primary structure, they share a highly conserved DNA-binding domain (DBD) that has been suggested to be zinc binding. Here we report the NMR solution structures of DBDs of two SBPs of Arabidopsis thaliana, SPL4 and SPL7. The two share essentially the same structural features. Each structure contains two zinc-binding sites consisting of eight Cys or His residues in a Cys3HisCys2HisCys or Cys6HisCys sequence motif in which the first four residues coordinate to one zinc and the last four coordinate to the other. These structures are dissimilar to other known zinc-binding structures, and thus represent a novel type of zinc-binding motif. The electrostatic profile on the surface suggested that a continuous region, including all the conserved basic residues, is involved in the DNA binding, the mode of which is likely to be novel as well.
Yamasaki
Kazuhiko
K
Age Dimension Research Center, National Insitute of Advanced Industrial Science and Technology, Tsukuba, Japan. k-yamasaki@aist.go.jp
Kigawa
Takanori
T
Inoue
Makoto
M
Tateno
Masaru
M
Yamasaki
Tomoko
T
Yabuki
Takashi
T
Aoki
Masaaki
M
Seki
Eiko
E
Matsuda
Takayoshi
T
Nunokawa
Emi
E
Ishizuka
Yoshiko
Y
Terada
Takaho
T
Shirouzu
Mikako
M
Osanai
Takashi
T
Tanaka
Akiko
A
Seki
Motoaki
M
Shinozaki
Kazuo
K
Yokoyama
Shigeyuki
S
D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000737:chemistry / Q000235:genetics; D029681:Arabidopsis Proteins / Q000737:chemistry* / Q000378:metabolism; D001665:Binding Sites; D002942:Circular Dichroism; D004247:DNA / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000378:metabolism; D046911:Macromolecular Substances; D008958:Models, Molecular; D008969:Molecular Sequence Data; D019906:Nuclear Magnetic Resonance, Biomolecular; D011485:Protein Binding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D016415:Sequence Alignment; D020349:Surface Plasmon Resonance; D014157:Transcription Factors / Q000737:chemistry* / Q000378:metabolism; D015032:Zinc / Q000378:metabolism*
D029681:Arabidopsis Proteins; D004268:DNA-Binding Proteins; D046911:Macromolecular Substances; C483287:SPL4 protein, Arabidopsis; C483288:SPL7 protein, Arabidopsis; D014157:Transcription Factors; D004247:DNA; D015032:Zinc