title: Xanthophyll cycle enzymes are members of the lipocalin family, the first identified from plants.
abstract: Violaxanthin de-epoxidase and zeaxanthin epoxidase catalyze the addition and removal of epoxide groups in carotenoids of the xanthophyll cycle in plants. The xanthophyll cycle is implicated in protecting the photosynthetic apparatus from excessive light. Two new sequences for violaxanthin de-epoxidase from tobacco and Arabidopsis are described. Although the mature proteins are well conserved, the transit peptides of these proteins are divergent, in contrast to transit peptides from other proteins targeted to the thylakoid lumen. Sequence analyses of both violaxanthin de-epoxidase and zeaxanthin epoxidase establish the xanthophyll cycle enzymes as members of the lipocalin family of proteins. The lipocalin family is a diverse group of proteins that bind small hydrophobic (lipophilic) molecules and share a conserved tertiary structure of eight beta-strands forming a barrel configuration. This is the first reported identification of lipocalin proteins in plants.
authors.affiliation: Department of Plant Molecular Physiology, University of Hawaii-Manoa, Honolulu, Hawaii 96822, USA.
authors.forename: R C
authors.initials: RC
authors.lastname: Bugos
authors.forename: A D
authors.initials: AD
authors.lastname: Hieber
authors.forename: H Y
authors.initials: HY
authors.lastname: Yamamoto
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000201:enzymology; D029681:Arabidopsis Proteins; D016384:Consensus Sequence; D018360:Crystallography, X-Ray; D018076:DNA, Complementary / Q000737:chemistry / Q000302:isolation & purification; D018744:DNA, Plant / Q000737:chemistry / Q000302:isolation & purification; D016208:Databases, Factual; D018545:Lactuca / Q000201:enzymology; D014975:Lutein / Q000378:metabolism*; D008565:Membrane Proteins / Q000235:genetics; D008969:Molecular Sequence Data; D010088:Oxidoreductases / Q000235:genetics / Q000378:metabolism*; D010940:Plant Proteins / Q000235:genetics; D010944:Plants / Q000201:enzymology*; D010947:Plants, Toxic; D017510:Protein Folding; D017433:Protein Structure, Secondary; D050765:Qa-SNARE Proteins; D017422:Sequence Analysis, DNA; D014026:Nicotiana / Q000201:enzymology
chemical_list: D029681:Arabidopsis Proteins; D018076:DNA, Complementary; D018744:DNA, Plant; C097724:KNOLLE protein, Arabidopsis; D008565:Membrane Proteins; D010940:Plant Proteins; D050765:Qa-SNARE Proteins; D010088:Oxidoreductases; C023290:violaxanthin de-epoxidase; C097153:zeaxanthin epoxidase; D014975:Lutein