ID #2278

Why does GTP hydrolyze when it does in the formation of a microtubule?

The delay in the hydrolysis of the GTP in the beta subunit allows for the potential of polymerization. Since GTP-bound tubulin has a high affinity for other tubulin, but GDP-bound tubulin does not, think about what would happen if the GTP was hydrolyzed immediately. 

If the GTP was hydrolyzed as soon as the tubulin was added to the microtubule, it would immediately lose its affinity for the microtubule and fall off before any other tubulin could get there and be added. But the delay before the GTP is hydrolyzed buys some time for more tubulin to be added if the local concentration of GTP-bound tubulin is high enough. 

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