Purification and spectroscopic analysis of 11S globulins from seeds of Cucumis sativus L

This study describes the purification and spectroscopic analysis of a trimeric (~ 180 kda) 11s globulin protein from the seeds of cucumis (c.) sativus l. the predominant seeds storage protein of c. sativus l. is a salt soluble globulin (~ 50 kda),which is composed of large (28-31 kda) and small (19-22 kda) subunits linked together through disulfide linkage. the n-terminal amino acid sequence of small subunit showed high homology (83%) to that of many monocotyledonous and dicotyledonous plant 11s globulins (also commonly known as cruciferins). further random amino acids sequences were obtained from maldi-q-tof ms/ms and multiple sequence alignment exhibited 72% sequence similarity with cruciferin of cucurbita maxima. c. sativus cruciferin (cscr) from seed was first partially purified by ammonium sulfate precipitation (40% saturation constant) and further by gel filtration chromatography. purified cscr exhibited a typical single polypeptide of approximately 50 kda monomeric protein under non-reduced condition of sds-page while produces two bands of major molecular weights of 28 kda (also called α-polypeptides) and 19 kda (β-polypeptides) under non-reduced conditions which is very much typical of 11s globulins and confirming the presence of disulfide linkages between two sub-units. highly purified cscr was produced in 25 mm phosphate buffer of ph 7.0 and subjected to dynamic light scattering (dls) measurement which showed the monodispersive nature of the 11s globulins with hydrodynamic radius of approx. 5.7 nm confirming the trimeric nature (~ 180 kda) of the protein. cscr was further subjected to circular dichroism (cd) spectra which indicated the presence of α-helices and β-sheets in the native conformation of approximately 180 kda proteins. this is a first report describing the purification and spectroscopic study of an 11s globulin/cruciferin protein from seeds of c. sativus.