1. ¹National Laboratory of Contraceptives and Devices Research, Shanghai Institute of Planned Parenthood Research, Shanghai 200032, China
2. ²College of Life Science, Shandong University, Ji' san 250100, China
3. ³Shandong University of Traditional Chinese Medicine, Ji' san 250014, China

Correspondence: Jia Ke TSO, E-mail: tso@sippr.stc.sh.cn, Tel: 021 64049215-3415

^*Co-first authors.

Received 19 April 2002; Revised 2 August 2002; Accepted 6 August 2002.

Abstract

p28, a 28kD protein from toad (Bufo bufo gargarizans) oocytes, was identified by using p13^suc1-agarose affinity chromatography. Sequence homology analysis of the full-length cDNA of p28(Gene Bank accession number: AF 314091) indicated that it encodes a protein containing 224 amino-acids with about 55% identities and more than 70% positives to human, rat or mouse UCH-L1, and contains homological functional domains of UCH family. Anti-p28 monoclonal antibody, on injecting into the oocytes, could inhibit the progesterone-induced resumption of meiotic division in a dose-dependent manner. The recombinant protein p28 showed similar SDS/PAGE behaviors to the native one, and promoted ubiquitin ethyl ester hydrolysis, a classical catalytic reaction for ubiquitin carboxyl terminal hydrolases (UCHs). The results in this paper reveal that a novel protein, p28, exists in the toad oocytes, is a UCH L1 homolog, was engaged in the process of progesterone-induced oocyte maturation possibly through an involvement in protein turnover and degradation.