Secondary structure of oleosins in oil bodies isolated from seeds of safflower (Carthamus tinctorius L.) and sunflower (Helianthus annuus L.).
Oil bodies were isolated from mature seeds of sunflower (Helianthus annuus L.) and safflower (Carthamus tinctorius L.). Oil body preparations containing only oleosin proteins could be obtained from safflower seeds by salt-washing followed by centrifugation on discontinuous sucrose density gradients. However, it was necessary to treat sunflower oil bodies with urea to obtain preparations of similar purity. Incubation of the oil bodies with proteinases gave two fragments with molecular masses of 6 and 8 kDa which were protected from digestion. These fragments represented the hydrophobic domain of the oleosins, as determined by N-terminal sequencing. Intact and proteinase-treated oil bodies of both species were analysed by Fourier-transform infrared spectroscopy, as dry films and in aqueous medium, the spectra being compared with those obtained for pure oil samples in order to identify the bands resulting from the oleosin proteins and protected peptides. This investigation showed that the hydrophobic domain of the oleosins in intact oil bodies is predominantly alpha-helical in structure and that the conformation was not greatly affected by washing the oil bodies with urea during preparation.
Institute of Arable Crops Research-Long Ashton Research Station, Department of Agricultural Sciences, University of Bristol, Long Ashton, Bristol BS41 9AF, UK.
D J
DJ
Lacey
N
N
Wellner
F
F
Beaudoin
J A
JA
Napier
P R
PR
Shewry
D000595:Amino Acid Sequence; D002499:Centrifugation, Density Gradient; D006368:Helianthus / Q000737:chemistry*; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010938:Plant Oils; D010940:Plant Proteins / Q000737:chemistry* / Q000302:isolation & purification; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D012450:Safflower Oil; D012639:Seeds / Q000737:chemistry*; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D017550:Spectroscopy, Fourier Transform Infrared; D000074242:Sunflower Oil; D014508:Urea
D010938:Plant Oils; D010940:Plant Proteins; D000074242:Sunflower Oil; C079350:oleosin, Helianthus annuus; D012450:Safflower Oil; D014508:Urea