Shark myelin basic protein: amino acid sequence, secondary structure, and self-association

Area of Science:

• Biochemistry
• Neuroscience
• Evolutionary Biology

Background:

• Myelin basic protein (MBP) is a key component of the myelin sheath in the central nervous system.
• Understanding variations in MBP across species can elucidate its structure-function relationships and evolutionary history.

Purpose of the Study:

• To purify and determine the amino acid sequence of myelin basic protein (MBP) from the Whaler shark (Carcharhinus obscurus).
• To compare the shark MBP sequence with other known MBPs, particularly bovine MBP.
• To investigate the structural and functional properties of shark MBP in solution.

Main Methods:

• Purification of MBP from shark brain extracts.
• Amino acid sequencing of the purified protein.
• Comparative sequence analysis with other MBPs.
• Secondary structure and self-association studies.

Main Results:

• The amino acid sequence of shark MBP was determined, showing 44% homology with bovine MBP.
• Shark MBP possesses distributed basic residues and lacks predicted ordered secondary structure segments, similar to other MBPs.
• The protein lacks a triproline sequence and has substitutions in the encephalitogenicity region, explaining its lack of activity.
• Despite primary structure differences, shark MBP exhibits solution properties comparable to bovine MBP.

Conclusions:

• Shark MBP represents a divergent form of the protein with unique sequence characteristics.
• Conserved solution properties suggest fundamental functional roles of MBP are maintained across species despite sequence variation.
• The study provides valuable data for understanding MBP evolution and the structural basis of its functions.