Surface properties of amaranth globulins

QUIROGA ALEJANDRA,; MARTINEZ NORA,; AÑON, MARÍA C.

Congreso; XL Anual meeting SAIB - SAB; 2004

Globulin-p and 11S-globulin are major amaranth storage proteins. They are extracted with different solvents, a saline neutral buffer for 11S-globulin and water for globulin-P. Both globulins are oligomers with similar subunit composition, globulin-p present a great trend to polymerization. Integrated by molecular units (MU) and aggregates (A). To study the different behavior of these globulins, in this work we analyze their surface characteristics and try to find structural differences. Globulin-P and 11S-globulin molecules were isolated and purified by isoelectric precipitation and gel filtration chromatography. Their solubility in different solvents was determined by the Lowry method and the composition of the soluble fractions was analyzed by gel filtration chromatography. The molecular surface charge was analyzed by ionic-exchange chromatography and surface hydrophobicity was evaluated using the fluorescent probe ANS. Both globulins, showed different solubility properties. Their chromatographic behavior was similar suggesting that there was no charge differences among them. On the other hand, (A) presented different surface hydrophobic properties from (MU) and 11S-globulin. (A) showed a higher number of hydrophobic sites per molecule and a lower hydrophobic association constant (Ka) than the other two molecules. These results indicated that (A) may have distinctive structural characteristics than (MU), whereas MU and 11S-globulin structure would resemble. On this basis we may propose that the amaranth storage globulins present slight structural differences related to their aggregation state which might confere them different protease accessibility during mobilization.