  2.5.1.83 | crystal structure both in the substrate-free form and in complex with 7,11-dimethyl-2,6,10-dodecatrien-1-yl diphosphate ammonium salt, an analog of farnesyl diphosphate, to 2.5 A and 2.7 A resolution, respectively. The structure of subunit HexB is composed of mostly antiparallel alpha-helices joined by connecting loops. Two aspartate-rich motifs and the other characteristic motifs in HexB are located around the diphosphate part of 7,11-dimethyl-2,6,10-dodecatrien-1-yl diphosphate. Despite the very low amino acid sequence identity and the distinct polypeptide chain lengths between subunits HexA and HexB, the structure of HexA is quite similar to that of HexB. The aliphatic tail of 7,11-dimethyl-2,6,10-dodecatrien-1-yl diphosphate is accommodated in a large hydrophobic cleft starting from HexB and penetrating to the inside of HexA suggesting that HexB catalyzes the condensation reactions and that HexA is directly involved in the product chain length control in cooperation with HexB |
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