title: Chrysanthemyl diphosphate synthase. The relationship among chain elongation, branching, and cyclopropanation reactions in the isoprenoid biosynthetic pathway.
abstract: The genes for chrysanthemyl diphosphate (CPP) synthase and farnesyl diphosphate (FPP) synthase from sagebrush, Artemisia tridentata spiciformis, were used to prepare a series of chimeric proteins to investigate the 1'-4 chain elongation, 1'-2 branching, and c1'-2-3 cyclopropanation reactions that join isoprenoid units to build more complex structures. The two genes were modified by site-directed mutagenesis to generate an identical set of six unique restriction sites at identical locations. The locations were selected to place a restriction site between each of the five conserved regions found in prenyltransferases that catalyze chain elongation. A series of chimeric proteins were generated by replacing amino acids in FPP synthase, beginning at the N-terminus of the enzyme, with increasing stretches of peptide from CPP synthase. An analysis of the products produced by the chimeras revealed a transition from 1'-4 chain elongation, to 1'-2 branching, and ultimately to c1'-2-3 cyclopropanation. These results demonstrate that the catalytic site for chain elongation, with minor modifications in its architecture, also catalyzes 1'-2 branching and c1'-2-3 cyclopropanation, and suggest that the branching and cyclopropanation reactions, in analogy to chain elongation, are electrophilic alkylations.
authors.affiliation: Department of Chemistry, University of Utah, 315 South 1400 East, Room 2020, Salt Lake City, Utah 84112, USA.
authors.forename: Hans K
authors.initials: HK
authors.lastname: Erickson
authors.forename: C Dale
authors.initials: CD
authors.lastname: Poulter
mesh_terms: D019883:Alkyl and Aryl Transferases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D019306:Artemisia / Q000201:enzymology* / Q000235:genetics; D003500:Cyclization; D051228:Geranyltranstransferase; D016297:Mutagenesis, Site-Directed; D011106:Polyisoprenyl Phosphates / Q000096:biosynthesis* / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism
chemical_list: D011106:Polyisoprenyl Phosphates; D011993:Recombinant Fusion Proteins; D019883:Alkyl and Aryl Transferases; D051228:Geranyltranstransferase