Isolation And Characterization Of Full Length Oleosin Cdna Clone From Oil Palm (Elaies Guineensis Jacq.) Kernel

Oleosins are embedded proteins in oil bodies. They have a structural role in stabilizing the triacylglycerol (TAG) / cytosol oil body interface in oil body biogenesis. A putative lipase attachment site on the oleosins implicates its involvement in the process of lipolysis (Hsieh and Huang, 2004). This lipolytic activity which produces free fatty acid (FFA) results in rancidity and impairment of oil palm quality. Oleosins also have been proposed as a carrier for the expression and purification of recombinant pharmaceuticals peptide. Besides, oleosins may also act as a natural emulsifying and stabilizing agent at an oil/water interface. A full length cDNA clone coding for oleosin from oil palm kernel was isolated through RACE-PCR (Rapid amplification of cDNA ends) technique. It has 381 bp of coding region with 45 bp of 5’ untranslated (UTR) region and 343 bp of 3’ UTR region. The longest open reading frame encodes a protein of 127 amino acids. The deduced protein sequence of oil palm oleosin cDNA exhibited high homology to the low molecular weight isoform of oleosin from Sesamum indicum (68%), Oryza sativa (67%), Hordeum vulgare (66%) Zea mays (65%) and Bromus secalinus (63%). The analysis on the amino acid composition of the deduced protein sequence of oil palm kernel oleosin showed that valine, leucine and alanine are the most predominant residues with low levels of asparagine, histidine, methionine and tryptophan. Valine, leucine and alanine are classified as nonpolar residues which occur mostly in the interior of a protein, out of contact with the aqueous solvent. The expression profile obtained in the Northern analysis showed that the oil palm oleosin expressed in both kernel and embryo tissues but no detectable signal in mesocarp, leaf and germinating seedling tissues. This result indicated that oleosins are found only in tissues that undergo dehydration. Thus, the oleosin transcript from oil palm is tissue-specific and its expression is tightly regulated.

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