A new epitope on human myelin basic protein arising from cleavage by a metalloendoprotease associated with brain myelin membranes
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Abstract:
Human brain myelin membranes were incubated to allow activity of an associated metalloendoprotease which cleaves myelin basic protein (MBP). A 10.3 kDa C-terminal fragment of MBP, peptide C, isolated from the incubation medium had a blocked N-terminal. After treatment with pyroglutamyl aminopeptidase, N-terminal sequencing indicated that Gln74 of MBP formed the N-terminal residue of peptide C. A rabbit antiserum was raised to a synthetic peptide containing the sequence Pyroglu-Lys-Ser-His-Gly-Arg, corresponding to the first six residues of peptide C. By immunoblotting this serum reacted with peptide C but not with intact MBP. The data indicate that cleavage of MBP by a myelin-associated protease engenders a new epitope.
Insights
A myelin-associated protease cleaves myelin basic protein (MBP), generating a new epitope. This cleavage creates a C-terminal fragment (peptide C) with a distinct N-terminal residue, identified via sequencing and antibody detection.
Area of Science:
- Neuroscience
- Biochemistry
- Proteomics
Background:
- Myelin basic protein (MBP) is a key component of the myelin sheath.
- Metalloproteases associated with myelin membranes can degrade MBP.
- Understanding MBP cleavage is crucial for myelin biology and neurological disorders.
Purpose of the Study:
- To identify the cleavage site and resulting fragment of MBP by a myelin-associated protease.
- To characterize the N-terminal sequence of the MBP fragment.
- To investigate the generation of new epitopes upon MBP cleavage.
Main Methods:
- Incubation of human brain myelin membranes to activate metalloendoprotease activity.
- Isolation and purification of the C-terminal MBP fragment (peptide C).
- N-terminal sequencing of peptide C after pyroglutamyl aminopeptidase treatment.
- Generation of rabbit antiserum against a synthetic peptide mimicking peptide C's N-terminus.
- Immunoblotting to detect reactivity with peptide C and intact MBP.
Main Results:
- A 10.3 kDa C-terminal fragment of MBP, termed peptide C, was isolated.
- N-terminal sequencing revealed Gln74 of MBP as the N-terminal residue of peptide C.
- An antiserum raised against a synthetic peptide corresponding to peptide C's N-terminus specifically reacted with peptide C, not intact MBP.
Conclusions:
- Cleavage of MBP by a myelin-associated protease generates a novel epitope at the N-terminus of the C-terminal fragment.
- This finding provides insights into post-translational modifications and protein processing within the myelin sheath.
- The generated epitope could serve as a biomarker for myelin degradation processes.