title: Evidence of a role for LytB in the nonmevalonate pathway of isoprenoid biosynthesis.
abstract: It is proposed that the lytB gene encodes an enzyme of the deoxyxylulose-5-phosphate (DOXP) pathway that catalyzes a step at or subsequent to the point at which the pathway branches to form isopentenyl diphosphate (IPP) and dimethylallyl diphosphate (DMAPP). A mutant of the cyanobacterium Synechocystis strain PCC 6803 with an insertion in the promoter region of lytB grew slowly and produced greenish-yellow, easily bleached colonies. Insertions in the coding region of lytB were lethal. Supplementation of the culture medium with the alcohol analogues of IPP and DMAPP (3-methyl-3-buten-1-ol and 3-methyl-2-buten-1-ol) completely alleviated the growth impairment of the mutant. The Synechocystis lytB gene and a lytB cDNA from the flowering plant Adonis aestivalis were each found to significantly enhance accumulation of carotenoids in Escherichia coli engineered to produce these colored isoprenoid compounds. When combined with a cDNA encoding deoxyxylulose-5-phosphate synthase (dxs), the initial enzyme of the DOXP pathway, the individual salutary effects of lytB and dxs were multiplied. In contrast, the combination of lytB and a cDNA encoding IPP isomerase (ipi) was no more effective in enhancing carotenoid accumulation than ipi alone, indicating that the ratio of IPP and DMAPP produced via the DOXP pathway is influenced by LytB.
authors.affiliation: Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, Maryland 20742, USA. fc18@umail.umd.edu
authors.forename: F X
authors.initials: FX
authors.lastname: Cunningham
authors.forename: T P
authors.initials: TP
authors.lastname: Lafond
authors.forename: E
authors.initials: E
authors.lastname: Gantt
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000458:Cyanobacteria / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics; D029968:Escherichia coli Proteins; D045782:Hemiterpenes; D008969:Molecular Sequence Data; D009943:Organophosphorus Compounds / Q000378:metabolism; D010088:Oxidoreductases; D010428:Pentosephosphates / Q000378:metabolism; D011401:Promoter Regions, Genetic; D011994:Recombinant Proteins / Q000378:metabolism; D015183:Restriction Mapping; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D014166:Transferases / Q000235:genetics / Q000378:metabolism
chemical_list: C109460:1-deoxylulose 5-phosphate; D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D045782:Hemiterpenes; D009943:Organophosphorus Compounds; D010428:Pentosephosphates; D011994:Recombinant Proteins; C004809:isopentenyl pyrophosphate; C043060:3,3-dimethylallyl pyrophosphate; D010088:Oxidoreductases; C109866:ispH protein, E coli; D014166:Transferases; C109461:deoxyxylulose-5-phosphate synthase