Purification and characterization of proline-rich proteins from developing embryos of the camel tick Hyalomma dromedarii

Abstract

The levels of acidic and basic proline-rich proteins in the camel tick Hyalomma dromedarii has been followed throughout embryogenesis. The developmental profiles of proline content in the crude protein fractions showed significant changes which would have to be of greater physiological consequences. During purification of FIIa to homogeneity the ion exchange chromatography step lead to separation of nine peaks where five of them were rich in proline. Gel filtration of FIIa peak 9 on Sephadex G-200 separated two forms (A and B) with proline/protein% of 23.75 and 2.35%, respectively. Peak A was proved to be pure by SDS-PAGE. FIb and FIIb were separated into four and five peaks by gel filtration on Sephadex G-200. Peaks 4 of FIb and FIIb were proved to be pure by SDS-PAGE with proline/protein% of 40.26 and 12.60%, respectively. FIIa, FIb and FIIb had different molecular weights (104 000–50 000, 24 000–23 000 and 16 000–17 000 for the native and denatured proteins, respectively), amino acid composition and carbohydrate/ protein%. The purified FIIa and FIIb had the ability to bind calcium and their maximum binding are exhibited at pH’s 3.5 and 6.5, respectively at 37°C. The effect of bivalent metals and proteolytic digestion on the binding of calcium to proline-rich proteins was studied.