Regulated interaction between polypeptide chain elongation factor-1 complex with the 26S proteasome during Xenopus oocyte maturation.
BACKGROUND
During Xenopus oocyte maturation, the amount of a 48 kDa protein detected in the 26S proteasome fraction (p48) decreased markedly during oocyte maturation to the low levels seen in unfertilized eggs. The results indicate that the interaction of at least one protein with the 26S proteasome changes during oocyte maturation and early development. An alteration in proteasome function may be important for the regulation of developmental events, such as the rapid cell cycle, in the early embryo. In this study, we identified p48.


RESULTS
p48 was purified by conventional column chromatography. The resulting purified fraction contained two other proteins with molecular masses of 30 (p30) and 37 (p37) kDa. cDNAs encode elongation factor-1gamma and delta were obtained by an immuno-screening method using polyclonal antibodies against purified p48 complex, which recognized p48 and p37. N-terminal amino acid sequence analysis of p30 revealed that it was identical to EF-1beta. To identify the p48 complex bound to the 26S proteasome as EF-1betagammadelta, antibodies were raised against the components of purified p48 complex. Recombinant EF-1 beta,gamma and delta were expressed in Escherichia coli, and an antibody was raised against purified recombinant EF-1gamma. Cross-reactivity of the antibodies toward the p48 complex and recombinant proteins showed it to be specific for each component. These results indicate that the p48 complex bound to the 26S proteasome is the EF-1 complex. MPF phosphorylated EF-1gamma was shown to bind to the 26S proteasome. When EF-1gamma is phosphorylated by MPF, the association is stabilized.


CONCLUSIONS
p48 bound to the 26S proteasome is identified as the EF-1gamma. EF-1 complex is associated with the 26S proteasome in Xenopus oocytes and the interaction is stabilized by MPF-mediated phosphorylation.
Tokumoto
Toshinobu
T
Department of Biology and Geosciences, Faculty of Science, Shizuoka University, Shizuoka 422-8529, Japan. sbttoku@ipc.shizuoka.ac.jp
Kondo
Ayami
A
Miwa
Junko
J
Horiguchi
Ryo
R
Tokumoto
Mika
M
Nagahama
Yoshitaka
Y
Okida
Noriyuki
N
Ishikawa
Katsutoshi
K
D000818:Animals; D046911:Macromolecular Substances; D016200:Maturation-Promoting Factor / Q000378:metabolism; D009865:Oocytes / Q000201:enzymology / Q000254:growth & development / Q000378:metabolism; D020648:Peptide Elongation Factor 1 / Q000378:metabolism*; D010447:Peptide Hydrolases / Q000378:metabolism*; D010766:Phosphorylation; D046988:Proteasome Endopeptidase Complex; D029867:Xenopus Proteins / Q000302:isolation & purification / Q000378:metabolism*; D014982:Xenopus laevis / Q000254:growth & development / Q000378:metabolism*
D046911:Macromolecular Substances; D020648:Peptide Elongation Factor 1; D029867:Xenopus Proteins; D016200:Maturation-Promoting Factor; D010447:Peptide Hydrolases; D046988:Proteasome Endopeptidase Complex; C061553:ATP dependent 26S protease