Do synapsin I and microtubule-associated proteins bind to a common site on polymerized tubulin?
Synapsin I plays an important role in the regulation of neurotransmitter release, since it binds to synaptic vesicles and to the cytoskeleton, and it bundles F-actin and microtubules. We have previously shown by tryptic digestion of synapsin I that a 44 kDa fragment contains a binding site for polymerized tubulin. In the present experiments, we test whether synapsin I and microtubule-associated proteins (MAPs) have the same or a different binding site on tubulin molecules. Our results show that heat stable MAPs do not compete with synapsin I for binding to taxol tubulin. In addition, subtilisin digestion of tubulin, which suppresses MAPs binding, does not abolish synapsin I cosedimentation with taxol tubulin. Thus, our results strongly suggest that synapsin I (as reported for kinesin) does not bind to the 4 kDa subtilisin digested C-terminal part of the tubulin molecule.
Aubert-Foucher
E
E
LBTM-CNRS, Université Claude Bernard Lyon I, Villeurbanne, France.
Deléage
G
G
Font
B
B
D000818:Animals; D001665:Binding Sites; D001667:Binding, Competitive; D002417:Cattle; D004355:Drug Stability; D006358:Hot Temperature; D066298:In Vitro Techniques; D008869:Microtubule-Associated Proteins / Q000378:metabolism*; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D011485:Protein Binding; D016704:Synapsins; D014404:Tubulin / Q000378:metabolism*
D008869:Microtubule-Associated Proteins; D009419:Nerve Tissue Proteins; D016704:Synapsins; D014404:Tubulin