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The crystal structure of a DNA-binding domain of PHO4 complexed with DNA at 2.8 A resolution revealed that the domain folds into a basic-helix-loop-helix (bHLH) motif with a long but compact loop that contains a short alpha-helical segment. This helical structure positions a tryptophan residue into an aromatic cluster so as to make the loop compact. PHO4 binds to DNA as a homodimer with direct reading of both the core E-box sequence CACGTG and its 3'-flanking bases. The 3'-flanking bases GG are recognized by Arg2 and His5. The residues involved in the E-box recognition are His5, Glu9 and Arg13, as already reported for bHLH/Zip proteins MAX and USF, and are different from those recognized by bHLH proteins MyoD and E47, although PHO4 is a bHLH protein.

Crystal structure of PHO4 bHLH domain-DNA complex: flanking base recognition., Shimizu T, Toumoto A, Ihara K, Shimizu M, Kyogoku Y, Ogawa N, Oshima Y, Hakoshima T, EMBO J. 1997 Aug 1;16(15):4689-97. PMID:9303313

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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Categories: Saccharomyces cerevisiae | Hakoshima, T. | Ihara, K. | Kyogoku, Y. | Ogawa, N. | Oshima, Y. | Shimizu, M. | Shimizu, T. | Toumoto, A. | Basic helix loop helix | Transcription factor | Transcription-dna complex