Detalle de: The β‐tubulin monomer release factor (p14) has homology with a region of the DnaJ protein

p14 is a molecular chaperone involved in β‐tubulin folding which catalyzes the release of β‐tubulin monomers from intermediate complexes. Here we demostrate that active p14 protein which we have purified from an overproducing Escherichia coli strain can also release ‐tubulin monomers from tubulin dimers in the presence of an additional cofactor (Z). Analysis of p14 secondary structure suggests that this protein may belong to a family of conserved proteins which share structural similarities with the J‐domain of DnaJ. We have constructed deletions and site‐directed mutations in the p14 gene. A single D to E mutation in the region shown in DnaJ to be an essential loop for its function affected the monomer‐release activity of p14. These results support the hypothesis that this p14 loop interacts with β‐tubulin in a similar fashion as DnaJ interacts with DnaK and suggest a possible role of p14 in the folding process.