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The PO protein. The major glycoprotein of peripheral nerve myelin
Abstract:
A glycoprotein, referred to as PO protein, was isolated from rabbit sciatic nerve myelin by gel filtration on Agarose 0.5 m in dodecyl sulfate. The purified myelin was first defatted and extracted at pH 2. The water-soluble proteins such as myelin basic protein and P2 protein were extracted leaving a glycoprotein-rich residue, from which the PO protein was isolated. The purified protein showed a single band on gel electrophoresis in dodecyl sulfate when stained with Coomassie Blue of periodic acid-Schiff reagent. The carbohydrate, comprising 6.3% by weight, appears to exist as a nonasaccharide unit having 3 mannose, 3 N-acetylglucosamine, 1 sialic acid, 1 galactose and 1 fucose residue. The polypeptide moiety has a high content of non-polar amino acids. A single amino acid, isoleucine, was found at the NH2-terminal end by dansyl and Edman procedures. The PO protein is the major protein of peripheral nerve myelin.
Insights
Researchers isolated the major peripheral nerve myelin protein, PO protein, from rabbit sciatic nerve. This glycoprotein is crucial for myelin structure and function.
Area of Science:
- Neuroscience
- Biochemistry
- Molecular Biology
Background:
- Peripheral nerve myelin is essential for nerve impulse conduction.
- Myelin composition includes structural proteins and lipids.
- Understanding myelin proteins aids in studying neurological disorders.
Purpose of the Study:
- To isolate and characterize the PO protein, a major component of peripheral nerve myelin.
- To elucidate the structural and compositional features of the PO protein.
Main Methods:
- Defatting and extraction of rabbit sciatic nerve myelin at pH 2.
- Gel filtration using Agarose 0.5 m in dodecyl sulfate for protein isolation.
- Gel electrophoresis and chemical analyses for protein and carbohydrate characterization.
Main Results:
- PO protein was successfully isolated as a purified glycoprotein.
- Electrophoresis revealed a single band, indicating high purity.
- Carbohydrate analysis showed a nonasaccharide unit (6.3% by weight); polypeptide moiety rich in non-polar amino acids.
- Isoleucine identified as the NH2-terminal amino acid.
Conclusions:
- PO protein is the predominant protein in peripheral nerve myelin.
- Its unique composition suggests a critical role in myelin structure and stability.
- Further research into PO protein may offer insights into myelin-related diseases.