Journal Article

Cloning and Secondary Structure Analysis of Caleosin, a Unique Calcium-Binding Protein in Oil Bodies of Plant Seeds

Jeff C.F. Chen, Corinne C.Y. Tsai and Jason T.C. Tzen

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 40, issue 10, pages 1079-1086
Published in print January 1999 | ISSN: 0032-0781
Published online January 1999 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/oxfordjournals.pcp.a029490
Cloning and Secondary Structure Analysis of Caleosin, a Unique Calcium-Binding Protein in Oil Bodies of Plant Seeds

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  • Biochemistry
  • Molecular and Cell Biology
  • Plant Sciences and Forestry

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Plant seed oil bodies comprise a matrix of triacylglycerols surrounded by a monolayer of phospholipids embedded with abundant oleosins and some minor proteins. Three minor proteins, temporarily termed Sops 1–3, have been identified in sesame oil bodies. A cDNA sequence of Sopl was obtained by PCR cloning using degenerate primers derived from two partial amino acid sequences, and subsequently confirmed via immunological recognition of its over-expressed protein in Escherichia coli. Alignment with four published homologous sequences suggests Sopl as a putative calcium-binding protein. Immunological cross-recognition implies that this protein, tentatively named caleosin, exists in diverse seed oil bodies. Caleosin migrated faster in SDS-PAGE when incubated with Ca2+. A single copy of caleosin gene was found in sesame genome based on Southern hybridization. Northern hybridization revealed that both caleosin and oleosin genes were concurrently transcribed in maturing seeds where oil bodies are actively assembled. Hydropathy plot and secondary structure analysis suggest that caleosin comprises three structural domains, i.e., an N-terminal hydrophilic calcium-binding domain, a central hydrophobic anchoring domain, and a C-terminal hydrophilic phosphorylation domain. Compared with oleosin, a conserved proline knot-like motif is located in the central hydrophobic domain of caleosin and assumed to involve in protein assembly onto oil bodies.

Keywords: Caleosin; Oil body; Proline knot; Seed; Sesame

Journal Article.  0 words. 

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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