Dataset Information

Secondary structure of oleosins in oil bodies isolated from seeds of safflower (Carthamus tinctorius L.) and sunflower (Helianthus annuus L.).

ABSTRACT: 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.

SUBMITTER: Lacey DJ

PROVIDER: S-EPMC1219711 | biostudies-other | 1998 Sep

REPOSITORIES: biostudies-other

ACCESS DATA

Similar Datasets

Project description:1. The average oil-body diameter in intact cells of developing linseed (Linum usitatissimum) and safflower (Carthamus tinctorius) cotyledons was similar (about 1.4 micrometer), and there was little change in size after oil bodies were isolated and repeatedly washed. 2. The glycerolipid composition of washed oil bodies from both developing and mature cotyledons of the two species was similar; oil bodies from ten different batches of cotyledons contained 4.3 +/- 0.16 mumol of 3-sn-phosphatidylcholine and 25.2 +/- 1.7 mumol of diacylglycerol per 1000 mumol of triacylglycerol. During four successive washings of a once-washed oil-body preparation, the proportion of diacylglycerol to triacylglycerol remained constant and that of 3-sn-phosphatidylcholine to triacylglycerol decreased by only 20%. 3. The protein content of thrice-washed oil bodies from the two species was similar, about 2.4% of the weight of glycerolipids, and appeared to be independent of the stage of cotyledon maturity. Sodium dodecyl sulphate/polyacrylamide-gel electrophoresis indicated that the protein of purified oil bodies from the two species consisted mainly of only four polypeptides and that two of the polypeptides from each species had apparent mol.wts. of 17500 and 15500. Similar patterns of polypeptides were obtained after the hydrolysis of the 15500-mol.wt. polypeptides from linseed and safflower oil bodies by Staphylococcus aureus V8 proteinase, whereas the proteolysis of the 17500-mol.wt. polypeptides from the two species produced different patterns of polypeptides. 4. The 3-sn-phosphatidylcholine in oil-body preparations was hydrolysed about 85% by bee-venom phospholipase A2 without any apparent coalescence of the oil bodies. Incubation with lipase from Rhizopus arrhizus caused rapid coalescence of the oil bodies, and this lipase appeared to initially hydrolyse diacylglycerols in preference to triacylglycerol. 5. Oil bodies from both species were almost completely dispersed in suspensions of pH between 7.1 and 8.3, but formed large aggregates at pH values between 6.7 and 3.9; pH-induced aggregation caused no coalescence. Aggregates formed under acidic conditions were dispersed by re-adjusting the pH of suspensions to 8.3. 6. A freeze-etch electron-microscopic examination of isolated oil bodies indicated that these organelles were bounded by some form of membrane with a particle-free outer surface.

Dataset Information

Secondary structure of oleosins in oil bodies isolated from seeds of safflower (Carthamus tinctorius L.) and sunflower (Helianthus annuus L.).

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets