Reicher, S., Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot, Israel, Institute of Animal Science, Agricultural Research Organization, Volcani Center, Bet Dagan, Israel
Ramos-Nieves, J.M., Department of Animal Science, Cornell University, Ithaca, NY 14853, United States
Hileman, S.M., Department of Physiology and Pharmacology, West Virginia University, Morgantown 26506, United States
Boisclair, Y.R., Department of Animal Science, Cornell University, Ithaca, NY 14853, United States
Gootwine, E., Institute of Animal Science, Agricultural Research Organization, Volcani Center, Bet Dagan, Israel
Gertler, A., Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot, Israel

Leptin (LEP) is a cytokine-like hormone proven to be involved in diverse biological processes. In livestock, it regulates feed intake, BW homeostasis, and energy balance, among other traits. Natural nonsynonymous genetic polymorphisms in the ovine leptin (oLEP) alter the biochemical and physiological characteristics of its gene products. Here we studied in vitro and in vivo the biochemical and physiological characteristics of recombinant hormones representing the oLEP and bovine leptin (bLEP) reference sequences of wild-type (WT) leptins (GenBank accession No. U84247 and U50365, respectively), oLEP and bLEP recombinant muteins carrying the R4C mutation, and oLEP recombinant hormones carrying the A59V and Q62R mutations, which were detected in bLEP. All proteins were purified to homogeneity as monomers and formed 1:1 molar ratio complexes with the chicken leptin-binding domain (LBD). Surface plasmon resonance experiments revealed that all protein variants exhibit reduced (P < 0.05) affinity to chicken (ch) and human (h) LBD compared with the WT oLEP and bLEP recombinant proteins. The ovine and bovine R4C muteins exhibited significantly (P < 0.05) greater induction of cell proliferation in a Baf/3 cell line bioassay, despite lower affinity toward both hLBD and chLBD. Intra-third cerebral ventricle infusion of oLEP and its 3 muteins in sheep resulted in reduced feed intake. However, the 3 tested muteins had a decreased (P < 0.05) inhibitory effect than the WT LEP. It was concluded that natural genetic polymorphisms in the bLEP are associated with variation in the biochemical and physiological properties of the protein. © 2012 American Society of Animal Science.