Partial purification of thrombopoietin using lectin chromatography

Area of Science:

• Hematology
• Biochemistry

Background:

• Thrombopoietin (TPO) is a key regulator of platelet production.
• Purification of TPO is essential for studying its biological functions and therapeutic potential.

Purpose of the Study:

• To develop an effective purification strategy for thrombopoietin (TPO) from thrombocytopenic rabbit plasma.
• To characterize the thrombopoietic activity of the partially purified TPO.

Main Methods:

• Partial purification of TPO using ammonium sulfate fractionation (60-80% saturation).
• Lectin chromatography employing wheat germ agglutinin (WGA) and concanavalin A (ConA) affinity columns.
• In vivo assay using 75Se-selenomethionine incorporation in mice to measure thrombopoietic activity.

Main Results:

• A 1000-fold increase in specific activity was achieved after WGA chromatography, reducing the minimum effective dose to 1.3 microgram/g body weight.
• An additional two-fold increase in specific activity was obtained with ConA chromatography, lowering the minimum effective dose to 0.65 microgram/g body weight.
• The overall purification yielded a 7000-fold increase in specific activity, though SDS-PAGE and GP-HPLC indicated the presence of multiple proteins.

Conclusions:

• Ammonium sulfate fractionation combined with sequential WGA and ConA lectin chromatography is an effective method for partially purifying thrombopoietic activity.
• The purified fraction stimulated thrombopoiesis without a significant increase in peripheral platelet count, suggesting complex regulatory mechanisms.
• Further purification steps are necessary to isolate homogeneous thrombopoietin, as the current fractions still contain numerous contaminating proteins.