The function of TUBA1B (tubulin alpha 1b, ENSG00000123416) is as follows. Tubulin is the major constituent of microtubules, protein filaments consisting of alpha- and beta-tubulin heterodimers (PubMed:38305685, PubMed:34996871, PubMed:38609661). Microtubules grow by the addition of GTP-tubulin dimers to the microtubule end, where a stabilizing cap forms (PubMed:38305685, PubMed:34996871, PubMed:38609661). Below the cap, tubulin dimers are in GDP-bound state, owing to GTPase activity of alpha-tubulin (PubMed:34996871, PubMed:38609661). {ECO:0000269|PubMed:34996871, ECO:0000269|PubMed:38305685, ECO:0000269|PubMed:38609661}.