THE BETA-TUBULIN MONOMER RELEASE FACTOR (P14) HAS HOMOLOGY WITH A REGION OF THE DNAJ PROTEIN

p14 is a molecular chaperone involved in beta-tubulin folding which ca talyzes the release of beta-tubulin monomers from intermediate complex es, Here we demostrate that active p14 protein which we have purified from an overproducing Escherichia call strain can also release beta-tu bulin monomers from tubulin dimers in the presence of an additional co factor (Z). Analysis of p14 secondary structure suggests that this pro tein may belong to a family of conserved proteins which share structur al similarities with the J-domain of DnaJ, We have constructed deletio ns and site-directed mutations in the p14 gene, A single D to E mutati on in the region shown in DnaJ to be an essential loop for its functio n affected the monomer-release activity of p14, These results support the hypothesis that this p14 loop interacts with beta-tubulin in a sim ilar fashion as DnaJ interacts with DnaK and suggest a possible role o f p14 in the folding process.