Development of oLH-S-S-gelonin conjugate bearing gelonin on β-subunit of oLH

Abstract

An attempt was made to cross-link the βoLH of ovine luteinizing hormone (oLH) to the ribosome inactivating protein, gelonin in order to develop an effective hormonotoxin for selective targeting to specific cells in the gonads. Three different molar ratios of oLH and N-succinimidyl-3-(2-pyridyldithio) propionate (SPDP) were used to activate the epsilon -NH₂ groups of oLH. The βoLH-SPDP derivatives recombine to αoLH and the purified recombinants retained substantial receptor binding, steroidogenic activity and immunoreactivity to native oLH. The purified (gel-filtration) βoLH-S-S-gelonin conjugates were allowed to recombine to αoLH, but an RP-HPLC analysis indicated that recombination did not take place. The failure to recombine may be due to: (i) the site of -NH₂ activation by SPDP may be different in βoLH from native oLH; (ii) the activation site may be in close proximity to the recombination site, which facilitates the recombination of α-subunit but

failed to reassociate to βoLH-S-S-gelonin conjugate and (iii) the introduction of gelonin (30 kDa basic protein) might have induced some steric hindrance for αoLH to recombine to the βoLH site which might have been masked in βoLH-S-Sgelonin conjugates.