title: Functional analysis of two solanesyl diphosphate synthases from Arabidopsis thaliana.
abstract: Solanesyl diphosphate (SPP) is regarded as the precursor of the side-chains of both plastoquinone and ubiquinone in Arabidopsis thaliana. We previously analyzed A. thaliana SPP synthase (At-SPS1) (Hirooka et al., Biochem. J., 370, 679-686 (2003)). In this study, we cloned a second SPP synthase (At-SPS2) gene from A. thaliana and characterized the recombinant protein. Kinetic analysis indicated that At-SPS2 prefers geranylgeranyl diphosphate to farnesyl diphosphate as the allylic substrate. Several of its features, including the substrate preference, were similar to those of At-SPS1. These data indicate that At-SPS1 and At-SPS2 share their basic catalytic machinery. Moreover, analysis of the subcellular localization by the transient expression of green fluorescent protein-fusion proteins showed that At-SPS2 is transported into chloroplasts, whereas At-SPS1 is likely to be localized in the endoplasmic reticulum in the A. thaliana cells. It is known that the ubiquinone side-chain originates from isopentenyl diphosphate derived from the cytosolic mevalonate pathway, while the plastoquinone side-chain is synthesized from isopentenyl diphosphate derived from the plastidial methylerythritol phosphate pathway. Based on this information, we propose that At-SPS1 contributes to the biosynthesis of the ubiquinone side-chain and that At-SPS2 supplies the precursor of the plastoquinone side-chain in A. thaliana.
authors.affiliation: Department of Biotechnology, Graduate School of Engineering, Osaka University, Suita, Yamadaoka, Japan.
authors.forename: Kazutake
authors.initials: K
authors.lastname: Hirooka
authors.forename: Yoshikazu
authors.initials: Y
authors.lastname: Izumi
authors.forename: Chung-Il
authors.initials: CI
authors.lastname: An
authors.forename: Yoshihisa
authors.initials: Y
authors.lastname: Nakazawa
authors.forename: Ei-ichiro
authors.initials: E
authors.lastname: Fukusaki
authors.forename: Akio
authors.initials: A
authors.lastname: Kobayashi
mesh_terms: D019883:Alkyl and Aryl Transferases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000201:enzymology*; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D002451:Cell Compartmentation; D003001:Cloning, Molecular; D017931:DNA Primers; D018076:DNA, Complementary; D049452:Green Fluorescent Proteins / Q000235:genetics; D007700:Kinetics; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction; D011993:Recombinant Fusion Proteins / Q000235:genetics; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity
chemical_list: D029681:Arabidopsis Proteins; D017931:DNA Primers; D018076:DNA, Complementary; D011993:Recombinant Fusion Proteins; D049452:Green Fluorescent Proteins; D019883:Alkyl and Aryl Transferases; C500830:SPS1 protein, Arabidopsis; C500831:SPS2 protein, Arabidopsis