The structure and properties of Napin-seed storage protein from rape (Brassica napus L.)

Abstract

Purification to homogeneity of 2S albumin storage protein from rape seeds (napin) was achieved and its secondary structure and conformational stability were characterised by circular dichroism (CD), and high-sensitivity differential scanning calorimetry (HS-DSC). Deconvolution of the far-UV CD spectrum of napin revealed about 25% of α-helix and 38% of β-sheet structure at neutral and slightly acid pH. HS-DSC data show a single peak of protein denaturation with maximum at 101°C and 88°C at pH 6.0 and 3.0, respectively. This discloses very high stability of napin tertiary structure. The thermal denaturation of napin is irreversible duc to secondary processes such as hydrophobic aggregation of the unfolded protein. The deconvolution of the transition profile at pH 3.0 carried out with assumption that napin aggregation does not contribute to the transition parameters allows to distinguish two constituent transitions which may be attributed to two different domains in napin folding.