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Corpus Systématique Animale

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On the role of the invariant glutamine at position 54 in the human choriogonadotropin ? subunit

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Springer (journals)
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Mots-clés d'auteur
  • gonadotropin
  • human choriogonadotropin
  • glycoprotein hormones
  • site-directed mutagenesis
Nom du fichier dans la ressource
  • Jianing Huang 1,2
  • David Puett 1,2
  • 1) Department of Biochemistry, University of Georgia, 30602, Athens, Georgia, USA
  • 2) Reproductive Sciences and Endocrinology Laboratory, Department of Biochemistry and Molecular Biology, University of Miami School of Medicine, 33101, Miami, Florida, USA

The twelve Cys and eight of the non-Cys residues are invariant in the glycoprotein hormone ? subunits from a variety of mammalian species. ?-Gin-54 of human lutropin (hLH) and choriogonadotropin (hCG) is one of these invariant amino acid residues. A single A?G mutation in the LH? gene of a patient presenting with hypogonadism resulted in the replacement of Gin-54 with Arg [1]. The authors also reported that an expressed mutant of hLH?, with Arg replacing Gin-54, associated with the ? subunit, but there was no demonstrable binding of the mutant hormone to receptor. We have replaced Gin-54 in hCG? with Glu and with Lys using site-directed mutagenesis. The expression plasmids pRSV-hCG? (wild-type and mutants) were transiently transfected into CHO cells containing a stably integrated gene for bovine ?, and the media were analyzed for holoproteins, which were characterizedin vitro using competitive binding and steroidogenic assays with MA-10 cells. hCG?(Glu-54) bound to ? almost as well as hCG? wild-type, and the resulting heterodimer competed with [125l]hCG binding to the LH/CG receptor and stimulated progesterone production to the same extent as the wild-type control. However, the apparent potencies, as judged by ED50s, were less than those of the wild-type control, the effect being more pronounced in binding than in steroidogenesis. In contrast, hCG?(Lys-54) associated very poorly with ?. Our results suggest that while Gin-54 in hCG? participates in receptor binding, its major function appears to involve ? binding. Such dual functionality leads to interesting models for holoprotein formation and receptor binding.

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  • 1 - health sciences
  • 2 - biomedical research
  • 3 - biochemistry & molecular biology
Catégories INIST
  • 1 - sciences appliquees, technologies et medecines
  • 2 - sciences biologiques et medicales
  • 3 - sciences medicales
  • 4 - immunopathologie
Catégories Scopus
  • 1 - Life Sciences ; 2 - Biochemistry, Genetics and Molecular Biology ; 3 - Cell Biology
  • 1 - Life Sciences ; 2 - Biochemistry, Genetics and Molecular Biology ; 3 - Clinical Biochemistry
  • 1 - Life Sciences ; 2 - Biochemistry, Genetics and Molecular Biology ; 3 - Molecular Biology
  • 1 - Health Sciences ; 2 - Medicine ; 3 - General Medicine
Catégories WoS
  • 1 - science ; 2 - cell biology
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Molecular and Cellular Biochemistry

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