title: Intrinsically unstructured N-terminal domain of bZIP transcription factor HY5.
abstract: The Arabidopsis HY5 protein is a basic leucine zipper (bZIP) transcription factor that promotes photomorphogenesis. HY5 binds directly to the promoters of light responsible element containing the G-box and thus regulates their transcriptional activity. The level and activity of HY5 are negatively regulated, in a light-dependent manner, by interaction with the COP1 protein, which targets HY5 for proteasome-mediated degradation in the nucleus. Despite its essential roles in plant development, no structural information exists for HY5. In this article, we report the first structural and biophysical characterization of HY5. Using limited proteolysis in combination with mass spectrometry, circular dichroism, and nuclear magnetic resonance spectroscopy, we have deduced that the N-terminal 77 amino acids of HY5 form a premolten globular structure, while amino acids 78-110, which constitute the basic region (BR) of the protein, exist in a molten globule state. Our studies also revealed that the overall structural features of full-length HY5 are dominated largely by the disordered N-terminal domain, despite the existence of a bZIP domain at its C-terminus. We propose that HY5 is a member of the intrinsically unstructured protein (IUP) family, and that HY5 functions as an unstructured protein and benefits from being the same, in vivo.
authors.affiliation: Department of Chemistry and National Creative Research Initiative Center, Korea Advanced Institute of Science and Technology, 373-1 Guseong-dong, Yuseong-gu, Daejon 305-701, Republic of Korea.
authors.forename: Mi-Kyung
authors.initials: MK
authors.lastname: Yoon
authors.forename: Jieun
authors.initials: J
authors.lastname: Shin
authors.forename: Giltsu
authors.initials: G
authors.lastname: Choi
authors.forename: Byong-Seok
authors.initials: BS
authors.lastname: Choi
mesh_terms: D000595:Amino Acid Sequence; D029681:Arabidopsis Proteins / Q000737:chemistry* / Q000302:isolation & purification; D050976:Basic-Leucine Zipper Transcription Factors / Q000737:chemistry* / Q000302:isolation & purification; D002942:Circular Dichroism; D009682:Magnetic Resonance Spectroscopy; D013058:Mass Spectrometry; D008957:Models, Genetic; D009687:Nuclear Proteins / Q000737:chemistry* / Q000302:isolation & purification; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification; D013696:Temperature
chemical_list: D029681:Arabidopsis Proteins; D050976:Basic-Leucine Zipper Transcription Factors; C109254:HY5 protein, Arabidopsis; D009687:Nuclear Proteins; D011994:Recombinant Proteins