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Myelin basic protein binds GTP at a single site in the N-terminus
C K Chan1, J Ramwani, M A Moscarello
1Hospital for Sick Children, Department of Biochemistry, Toronto, Ontario, Canada.
Biochemical and Biophysical Research Communications
|May 16, 1988
Summary
Myelin basic protein from human brain undergoes ADP-ribosylation by Cholera toxin. This protein binds azido-GTP at a specific N-terminal site, indicating a potential functional role.
Area of Science:
- Neuroscience
- Biochemistry
- Molecular Biology
Background:
- Myelin basic protein (MBP) is a key component of the myelin sheath in the central nervous system.
- ADP-ribosylation is a post-translational modification involved in various cellular processes.
- Cholera toxin and Pertussis toxin are bacterial toxins that ADP-ribosylate specific proteins.
Purpose of the Study:
- To investigate the susceptibility of human brain myelin basic protein to ADP-ribosylation by bacterial toxins.
- To identify the binding site and characteristics of guanosine triphosphate (GTP) binding to MBP.
Main Methods:
- Purification of myelin basic protein from normal human brain.
- Incubation of MBP with Cholera toxin and Pertussis toxin.
- Binding assays using azido-GTP, GppNHp, and GTPγS.
Main Results:
- Myelin basic protein was ADP-ribosylated by Cholera toxin, but not by Pertussis toxin.
- MBP exhibited specific binding of azido-GTP at a single site within the N-terminal tetrapeptide, specifically at the glutamine (Gln) residue.
- GppNHp partially inhibited azido-GTP binding, while GTPγS completely inhibited it.
Conclusions:
- Human brain myelin basic protein is a substrate for Cholera toxin-mediated ADP-ribosylation.
- MBP possesses a specific GTP-binding site in its N-terminus.
- The functional significance of this GTP binding remains to be elucidated.