RESUMO
CGß subunits comprise a unique carboxyl-terminal peptide (CTP) that has multiple O-linked glycans and extends serum half-life of the protein. It has evolved by incorporating a previously untranslated region of the LHß gene into the reading frame. Although CTP-like sequences are encrypted in the LHß genes of several mammals, the CGß subunit developed only in primates and equids. To study this restriction in evolution, we examined whether the cryptic CTP decoded from the bovine LHß gene (boCTP) possesses key characteristics of the human (h) CGß-CTP. The boCTP does not impede several crucial aspects of hormone biosynthesis, but compared to the hCGß-CTP, the stretch lacks O-glycans and determinants for circulatory survival. O-glycan deficiency and the associated incapacity to extend serum half-life is a major drawback of the boCTP. This may explain why LH did not evolve into CG in ruminants and consequently alternative mechanisms evolved to delay luteolysis early in gestation.