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Crystal structure of HY5 leucine zipper homodimer from Arabidopsis thalianaCrystal structure of HY5 leucine zipper homodimer from Arabidopsis thaliana
Structural highlights
FunctionHY5_ARATH Transcription factor that promotes photomorphogenesis in light. Acts downstream of the light receptor network and directly affects transcription of light-induced genes. Specifically involved in the blue light specific pathway, suggesting that it participates in transmission of cryptochromes (CRY1 and CRY2) signals to downstream responses. In darkness, its degradation prevents the activation of light-induced genes. Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedThe leucine zipper (LZ) domain of the HY5 transcription factor from Arabidopsis thaliana has unique primary structural properties, including major occupation by the Leu residues as well as two buried polar residues in the a positions and a localized distribution of charged and polar residues in the first three heptad repeats. In this study, we solved the crystal structure of the HY5 LZ domain and show that the peculiarities in the primary sequence yield unusual structural characteristics. For example, the HY5 LZ domain exhibits a bipartite charge distribution characterized by a highly negative electrostatic surface potential in its N-terminal half and a nearly neutral potential in its C-terminal half. The LZ N-terminal region also contains two consecutive putative trigger sites for dimerization of the coiled coils. In addition, two buried asparagines at a positions 19 and 33 in the HY5 LZ domain display distinct modes of polar interaction. Whereas Asn(19) shows a conformational flip-flop, Asn(33) is engaged in a permanent hydrogen bond network. CD spectropolarimetry and analytical ultracentrifugation experiments performed with versions of the HY5 LZ domain containing mutations in the a positions yielded further evidence that position a amino acid residues are crucial for achieving an oligomeric state and maintaining stability. However, a low correlation between position a amino acid preference, core packing geometry, and rotamer conformations suggests that the oligomeric state of the LZ domain is not governed entirely by known structural properties. Taken together, our results suggest structural factors conferring conformational integrity of the HY5 LZ homodimer that are more complicated than proposed previously. Structural basis for the conformational integrity of the Arabidopsis thaliana HY5 leucine zipper homodimer.,Yoon MK, Kim HM, Choi G, Lee JO, Choi BS J Biol Chem. 2007 Apr 27;282(17):12989-3002. Epub 2007 Jan 29. PMID:17261584[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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