A cDNA clone encoding for a Prothymosin alpha (Prot-alpha) has been isolated and 
characterized from the testis of the frog Rana esculenta. Frog Prothymosin alpha 
(fProt-alpha) predicted a 109 amino acid protein with a high homology to the 
mammalian Prot-alpha. fProt-alpha contains 28 aspartic and 25 glutamic acid 
residues and presents the typical basic KKQK amino acid sequence in the close 
carboxyl terminal region. Northern blot analysis revealed that fProt-alpha is 
highly expressed in the testis. A different expression of fProt-alpha transcript 
was found during the frog reproductive cycle with a peak in September/October in 
concomitance with germ cell maturation, strongly suggesting a role for this 
protein in the testicular activity. In situ hybridization evidenced that the 
only germ cells expressing fProt-alpha are the primary and secondary 
spermatocytes; in addition, the hybridization signal was stronger in the October 
testis. Taken together, our findings indicate that fProt-alpha might contribute 
to the efficiency of frog spermatogenesis with a role during the meiosis. This 
study is the first report on the isolation and characterization of a Prot-alpha 
in a non-mammalian vertebrate. In addition, our results indicate that the testis 
of the frog R. esculenta may be a useful model to increase the knowledge 
concerning the physiological role of Prot-alpha in vertebrates.