Factors regulating microtubule structure--a minireview.

The pathway of tubulin assembly is controlled by a lot of effectors. We summarize some of these effectors favouring the formation of microtubules or inducing several MT-aberrant, polymorphic structures. Both in vivo and in vitro, microtubules with different protofilament numbers were found. In vivo, microtubules are composed of 11-16 protofilaments. The protofilament number of microtubules formed in vitro varies from 8-17. We describe some effectors responsible for the diversity of the protofilament number in microtubules. Moreover, differences in the amino acid sequences of distinct tubulins should be taken into account, too. The protofilament number of an established microtubule can be still altered if activities of effectors or microenvironmental conditions are changed. Thus, the protofilament number of microtubules is a dynamic property based on the permanent tubulin exchange.