Glycogen-bound protein in lower eukaryote and prokaryote

Area of Science:

• Biochemistry
• Molecular Biology
• Microbiology

Background:

• Proteoglycogen, a complex of protein and polysaccharide, has been primarily studied in higher eukaryotes.
• Its presence and function in primitive unicellular organisms remain largely unexplored.

Purpose of the Study:

• To investigate the existence and characteristics of proteoglycogen in the primitive fungus Neurospora crassa.
• To identify and characterize the protein component of proteoglycogen in N. crassa and compare it with findings in bacteria.

Main Methods:

• Purification of the proteoglycogen fraction from Neurospora crassa.
• Radioiodination of the purified fraction using [125I]iodide.
• Amylolysis to isolate the protein moiety.
• NH2-terminal amino acid sequencing of the isolated protein.
• Investigation of glycogen-binding proteins in Escherichia coli.

Main Results:

• A labeled 31 kDa-protein was isolated from the proteoglycogen of N. crassa after radioiodination and amylolysis.
• The NH2-terminal amino acid sequence of 10 residues of this 31 kDa-protein was determined.
• A similar 31 kDa-protein was found to be bound to glycogen in Escherichia coli.

Conclusions:

• This study reports the first identification of proteoglycogen in a primitive unicellular organism, Neurospora crassa.
• The findings suggest that glycogen-binding proteins of approximately 31 kDa are conserved across different primitive life forms, including fungi and bacteria.
• The discovery of proteoglycogen in N. crassa and E. coli broadens the known phylogenetic distribution of these protein-carbohydrate complexes.