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 catalyzes the release of beta-tubulin monomers from intermediate complexes. Here we demonstrate that active p14 protein which we have purified from an overproducing Escherichia coli strain can also release beta-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 beta-tubulin in a similar fashion as DnaJ interacts with DnaK and suggest a possible role of p14 in the folding process.
Llosa
M
M
Departamento de Biología Molecular, Facultad de Medicina, Universidad de Cantabria, Santander, Spain.
Aloria
K
K
Campo
R
R
Padilla
R
R
Avila
J
J
Sánchez-Pulido
L
L
Zabala
J C
JC
D000595:Amino Acid Sequence; D018833:Chaperonins; D019281:Dimerization; D029968:Escherichia coli Proteins; D050956:HSP40 Heat-Shock Proteins; D006360:Heat-Shock Proteins / Q000737:chemistry*; D008958:Models, Molecular; D018832:Molecular Chaperones / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D017510:Protein Folding; D017433:Protein Structure, Secondary; D011506:Proteins / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry; D017384:Sequence Deletion; D017386:Sequence Homology, Amino Acid; D014404:Tubulin / Q000737:chemistry* / Q000378:metabolism
C494635:DnaJ protein, E coli; D029968:Escherichia coli Proteins; D050956:HSP40 Heat-Shock Proteins; D006360:Heat-Shock Proteins; D018832:Molecular Chaperones; D011506:Proteins; D011994:Recombinant Proteins; D014404:Tubulin; C087414:chaperonin cofactor A; D018833:Chaperonins