Low molecular weight albumins from sunflower seed: identification of a methionine-rich albumin

The small M r , proteins of sunflower seed ( Helianthus annuus) are soluble in 60% (by vol) methanol. These proteins, classified as albumins on the basis of their solubility in water, were isolated from a salt extract of sunflower seed by precipitating the 11S globulins with 60% (by vol) methanol an...

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Bibliographic Details
Published in:Phytochemistry (Oxford) 1990, Vol.29 (9), p.2805-2810
Main Authors: Kortt, Alexander A., Caldwell, J.Bruce
Format: Article
Language:English
Subjects:
amino acid compositions
Biological and medical sciences
Compositae
Fundamental and applied biological sciences. Psychology
Helianthus annuus
methionine-rich albumin
Plant physiology and development
sunflower albumins
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Summary:The small M r , proteins of sunflower seed ( Helianthus annuus) are soluble in 60% (by vol) methanol. These proteins, classified as albumins on the basis of their solubility in water, were isolated from a salt extract of sunflower seed by precipitating the 11S globulins with 60% (by vol) methanol and were resolved into eight distinct components by reversed-phase HPLC. Electrophoresis showed that each fraction contained a single polypeptide chain with an apparent M r , in the range 10 000–18 000. The individual sunflower albumins are basic proteins with distinct amino acid compositions. The major albumins (4–8) contain high contents of glutamine/glutamic acid, asparagine/aspartic acid, arginine and cysteine, characteristic of the 2S class of seed storage proteins. One exception was the small glutamine/glutamic acid content of albumin 6. Two of the sunflower albumins (7 and 8) with M r - 10 000 were methionine-rich proteins containing 16 residues per cent methionine as well as eight residues per cent cysteine. These sulphur-rich proteins constitute some 7% of the total salt extractable seed protein. A method for the preparation of these two albumins using a reversed-phase Sep-pak cartridge is described.
ISSN:0031-9422
1873-3700
DOI:10.1016/0031-9422(90)87080-E