Non-enzymatic glycosylation influences Hb S polymerization

Area of Science:

• Biochemistry
• Hematology
• Molecular Biology

Background:

• Sickle cell anemia is a genetic blood disorder caused by abnormal hemoglobin S (Hb S).
• Glycosylation, the attachment of sugars, is a post-translational modification that can alter protein function.

Purpose of the Study:

• To isolate and characterize in vivo glycosylated components of Hb S from sickle cell anemia patients.
• To investigate the impact of glycosylation on Hb S properties, including 2,3-DPG binding, solubility, and gelling.

Main Methods:

• Affinity and cation exchange chromatography were used to isolate glycosylated hemoglobin fractions (GHb) from red cell hemolysates.
• Isolated fractions included Hb SIc, Hb So-glycosylated, and Hb So-nonglycosylated.

Main Results:

• Glycosylated hemoglobin S (GHb) comprised Hb SIc (33%) and Hb So-glycosylated (42%), with minor amounts of glycosylated Hb F and Hb A2.
• Glycosylation affected 2,3-DPG binding only in Hb SIc, not in Hb So-glycosylated.
• Both Hb SIc and Hb So-glycosylated exhibited increased solubility and higher minimum gelling concentrations compared to non-glycosylated Hb So.

Conclusions:

• In vivo glycosylation of Hb S modifies specific sites involved in intermolecular interactions.
• These modifications influence Hb S solubility and gelling properties, suggesting a potential role in sickle cell disease pathophysiology.