title: Significance of charge on lysine residue of ovine luteinizing hormone on immunological and biological properties of the hormone.
abstract: In order to understand the significance of positive charge of lysine residues of ovine luteinizing hormone (oLH) on immunological and biological activity, the epsilon-NH2 group(s) of ovine LH were sequentially modified with 2-iminothiolane (2IT) that preserves the positive charge of the lysine while the overall charge of the hormone remains unchanged. These studies have also been compared with the oLH modified by N-succinimidyl 3-(2 pyridyldithio) propionate (SPDP) and succinimidyl 6-[3-(2-pyridyldithio)propionamido]hexanoate (LC-SPDP) that abolish positive charge of lysine residues. The modification primarily occurs in the alpha-subunit. Sequential modification led to progressive reduction in receptor binding and immunological activities. However, the steroidogenic activity was substantially retained. The immunoreactivity and receptor binding properties of 2IT modified oLH (oLH-2IT) were less affected when compared to SPDP (oLH-SPDP) or LC-SPDP (oLH-LC-SPDP) modified derivatives suggesting that increase in hydrophobic carbon chain in oLH-LC-SPDP molecule resulted in drastic inhibition in immunological and biological properties. But the steroidogenic potential of oLH-2IT, oLH-LC-SPDP or oLH-SPDP was relatively comparable. This suggests that a single -NH2 group modification with 2IT would generate the site in the hormone for conjugation to the toxin/carrier proteins that may retain better immunological and biological activity compared to that of SPDP or LC-SPDP modified oLH.
authors.affiliation: Hormone Biochemistry Laboratory, North-Eastern Hill University, Meghalaya, India. vs56@hotmail.com
authors.forename: V
authors.initials: V
authors.lastname: Singh
authors.forename: R C
authors.initials: RC
authors.lastname: Singh
authors.forename: R K
authors.initials: RK
authors.lastname: Dubey
mesh_terms: D000818:Animals; D007986:Luteinizing Hormone / Q000737:chemistry / Q000276:immunology / Q000502:physiology*; D008239:Lysine / Q000737:chemistry*; D012756:Sheep
chemical_list: D007986:Luteinizing Hormone; D008239:Lysine