Isolation and Characterisation of Platelet “Tubulin”, a Sub-Unit Protein of the Microtubules

From studies with whole platelets using microtubule binding agents such as colchicine and vinblastine, it appears that the microtubule have a cytoskeletal function and may be involved in shape changes, intracellular transport and other forms of cell motile activity.

A microtubule subunit protein, “tubulin”, has been isolated from pig platelets and shown to have properties similar to tubulins from cilia, flagella and mammalian brains. The protein binds ^SH-colchicine, has a sedimentation constant as the dimer of about 6 S and the monomer (MW±55,000) coelectrophoreses with rat, rabbit and guineapig brain tubulins, running in acrylamide gels as a closely spaced doublet similar to the α and β components of brain tubulin. Some higher molecular weight presumptive dyrnein components are also present. The polymer formed during a temperature dependent “in vitri.)” assembly procedure has been studied by electron microscopy. Long linear aggregates with side to side association can be seen, resembling the microtubule subfilamentous structures seen in whole platelet preparations.

 

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