Five structurally related proteins from affinity-purified Maclura pomifera lectin

Area of Science:

• Biochemistry
• Molecular Biology
• Carbohydrate Chemistry

Background:

• Maclura pomifera lectin (MPL) is a protein isolated from the Osage orange tree.
• Lectins are proteins known for their ability to bind carbohydrates, playing roles in biological recognition.

Purpose of the Study:

• To characterize the molecular structure and heterogeneity of affinity-purified Maclura pomifera lectin (MPL).
• To investigate the relationship between MPL's polypeptide chains and its functional properties.

Main Methods:

• Gel filtration chromatography to determine molecular weight.
• Dissociation of MPL into polypeptide subunits.
• Ion-exchange chromatography (DEAE-cellulose) to resolve MPL components.
• Discontinuous polyacrylamide gel electrophoresis (PAGE) for protein separation.
• Hemagglutination assays to assess erythrocyte binding.

Main Results:

• Affinity-purified MPL behaves as a single protein (approx. 40,000 Daltons) on gel filtration.
• MPL dissociates into two distinct polypeptide chains (approx. 10,000 Daltons each).
• Ion-exchange chromatography reveals five structurally related MPL components with varying subunit proportions.
• Two tetrameric lectins, each comprising only one type of polypeptide chain, show distinct chromatographic and electrophoretic behavior.
• These distinct lectin forms exhibit identical hemagglutination activity and carbohydrate-binding interactions.

Conclusions:

• Maclura pomifera lectin (MPL) is composed of two dissimilar polypeptide subunits.
• Structural variations in subunit composition lead to multiple MPL forms.
• Despite structural differences, these MPL variants retain similar carbohydrate-binding and hemagglutination functions.