Steroleosin, a Sterol-Binding Dehydrogenase in Seed Oil Bodies
Open Access
- 1 April 2002
- journal article
- Published by Oxford University Press (OUP) in Plant Physiology
- Vol. 128 (4), 1200-1211
- https://doi.org/10.1104/pp.010982
Abstract
Besides abundant oleosin, three minor proteins, Sop 1, 2, and 3, are present in sesame (Sesamum indicum) oil bodies. The gene encoding Sop1, named caleosin for its calcium-binding capacity, has recently been cloned. In this study, Sop2 gene was obtained by immunoscreening, and it was subsequently confirmed by amino acid partial sequencing and immunological recognition of its overexpressed protein in Escherichia coli. Immunological cross recognition implies that Sop2 exists in seed oil bodies of diverse species. Along with oleosin and caleosin genes, Sop2 gene was transcribed in maturing seeds where oil bodies are actively assembled. Sequence analysis reveals that Sop2, tentatively named steroleosin, possesses a hydrophobic anchoring segment preceding a soluble domain homologous to sterol-binding dehydrogenases/reductases involved in signal transduction in diverse organisms. Three-dimensional structure of the soluble domain was predicted via homology modeling. The structure forms a seven-stranded parallel β-sheet with the active site, S-(12X)-Y-(3X)-K, between an NADPH and a sterol-binding subdomain. Sterol-coupling dehydrogenase activity was demonstrated in the overexpressed soluble domain of steroleosin as well as in purified oil bodies. Southern hybridization suggests that one steroleosin gene and certain homologous genes may be present in the sesame genome. Comparably, eight hypothetical steroleosin-like proteins are present in the Arabidopsis genome with a conserved NADPH-binding subdomain, but a divergent sterol-binding subdomain. It is indicated that steroleosin-like proteins may represent a class of dehydrogenases/reductases that are involved in plant signal transduction regulated by various sterols.Keywords
This publication has 34 references indexed in Scilit:
- Guinea pig 11β-hydroxysteroid dehydrogenase type 1: primary structure and catalytic properties☆Steroids, 2000
- Oleosins and Oil Bodies in Seeds and Other OrgansPlant Physiology, 1996
- Structure, function and biogenesis of storage lipid bodies and oleosins in plantsProgress in Lipid Research, 1993
- Surface structure and properties of plant seed oil bodiesThe Journal of cell biology, 1992
- Basic local alignment search toolJournal of Molecular Biology, 1990
- The helical hydrophobic moment: a measure of the amphiphilicity of a helixNature, 1982
- A simple method for displaying the hydropathic character of a proteinJournal of Molecular Biology, 1982
- Relation between structure and function of α/β–protejnsQuarterly Reviews of Biophysics, 1980
- Spherosome MembranesPlant Physiology, 1972
- Cleavage of Structural Proteins during the Assembly of the Head of Bacteriophage T4Nature, 1970