title: Structure-function studies of human leptin.
abstract: To elucidate the structural requirement of human leptin for its functions, the wild-type, mutant-type, C-terminal deletion, and N-terminal deletion were expressed in Escherichia coli and purified in soluble forms. These leptin analogs were intracerebroventrically injected into C57BL/6J ob/ob mice, and their in vivo biological activities were evaluated. The mutant-type leptin lacking a C-terminal disulfide bond reduced food intake at doses of more than 15 pmol/mouse, which was as effective as the wild-type leptin. C-terminal deletion without the loop structure, also significantly, but to a lesser extent, reduced food intake at doses of more than 90 pmol/mouse. However, N-terminal deletions showed no effect on food intake. We also evaluated the effects of the leptin analogs on radiolabeled leptin binding to its receptor in the choroid plexus using autoradiography. An excess of unlabeled mutant-type leptin as well as wild-type leptin led to complete inhibition of binding. C-terminal deletions led to weak inhibitory activity, whereas N-terminal deletions caused no inhibitory activity. These results clearly demonstrate that the N-terminal region of leptin is essential for both its biological and receptor binding activities. The amino acid sequence of the C-terminal loop structure is also important for enhancing these actions, whereas the C-terminal disulfide bond is not needed.
authors.affiliation: Research and Development Diagnostic Science Division, Osaka 566-0022, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Imagawa
authors.forename: Y
authors.initials: Y
authors.lastname: Numata
authors.forename: G
authors.initials: G
authors.lastname: Katsuura
authors.forename: I
authors.initials: I
authors.lastname: Sakaguchi
authors.forename: A
authors.initials: A
authors.lastname: Morita
authors.forename: S
authors.initials: S
authors.lastname: Kikuoka
authors.forename: Y
authors.initials: Y
authors.lastname: Matumoto
authors.forename: T
authors.initials: T
authors.lastname: Tsuji
authors.forename: M
authors.initials: M
authors.lastname: Tamaki
authors.forename: K
authors.initials: K
authors.lastname: Sasakura
authors.forename: H
authors.initials: H
authors.lastname: Teraoka
authors.forename: K
authors.initials: K
authors.lastname: Hosoda
authors.forename: Y
authors.initials: Y
authors.lastname: Ogawa
authors.forename: K
authors.initials: K
authors.lastname: Nakao
mesh_terms: D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism*; D004220:Disulfides / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004926:Escherichia coli / Q000235:genetics; D006801:Humans; D007276:Injections, Intraventricular; D020738:Leptin; D051379:Mice; D008810:Mice, Inbred C57BL; D008817:Mice, Mutant Strains; D016296:Mutagenesis; D009765:Obesity / Q000378:metabolism*; D011485:Protein Binding; D011489:Protein Denaturation; D011506:Proteins / Q000235:genetics / Q000494:pharmacology*; D011956:Receptors, Cell Surface; D054411:Receptors, Leptin; D011994:Recombinant Proteins / Q000494:pharmacology; D017384:Sequence Deletion; D012995:Solubility; D013329:Structure-Activity Relationship; D013438:Sulfhydryl Compounds / Q000378:metabolism
chemical_list: D002352:Carrier Proteins; D004220:Disulfides; C515448:LEPR protein, human; D020738:Leptin; D011506:Proteins; D011956:Receptors, Cell Surface; D054411:Receptors, Leptin; D011994:Recombinant Proteins; D013438:Sulfhydryl Compounds; C515447:leptin receptor, mouse