A conserved small GTP-binding protein Alp41 is essential for the cofactor-dependent biogenesis of microtubules in fission yeast

The proper folding of tubulins and their incorporation into microtubules co nsist of a series of reactions. in which evolutionarily conserved proteins, cofactors A to E, play a vital role. We have cloned a fission east gene (a lp41(+)) which encodes a highly conserved small GTP-binding protein homolog ous to budding yeast CIN4 and human ARF-like Arl2. alp41(+) is essential, d isruption of which results in microtubule dysfunction and growth polarity d efects. Genetic analysis indicates that Alp41 plays a crucial role in the c ofactor-dependent pathway, in which it functions upstream of the cofactor D homologue Alp1(D) and possibly in concert with Alp21(E) (C) 2000 Federatio n of European Biochemical Societies.