| Abstract: | | 1. | A simple and rapid method is described for the isolation and purification of oocyte vitellin ofLocusta migratoria. The isolated protein has been shown to be homogenous by polyacrylamide gel electrophoresis, isoelectric focusing, sedimentation analysis and in the Ouchterlony test. | | 2. | The yolk protein stains with Sudan black and lipid crimson, it reacts with the PAS-reagent and is thus a lipo-glycoprotein. Its isoelectric point is at pH 6.9. At neutral pH the protein is poorly soluble in solutions of low ionic strength, but is easily soluble at alkaline pH. At neutral or acidic pH the yolk protein tends to aggregate to a dimer and a trimer. | | 3. | The amino acid composition shows a high content of aspartic and glutamic acid or their amides and a low percentage of sulphur containing amino acids. As N-terminal amino acids alanine and aspartic acid are found. | | 4. | The yolk protein consists of several non-identical subunits. In polyacrylamide gel electrophoresis with sodium dodecyl sulphate subunits of 55,000, 65,000, 110,000, 120,000 and 130,000 Daltons are found. The molecular weight was determined to 530,000±30,000 Daltons, the sedimentation coefficient ass20,w=16.3±0.02 (corrected). The frictional ratio isf/f0=1.105, the molar extinction coefficient at 280 nm is 4.2×105 (=0.91 per mg protein). |
All subunits stain as glycoproteins; the total sugar content was determined as 11%. |
