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This Article Full Text Full Text (PDF) All Versions of this Article: JOE-09-0141v1 203/1/167    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Galet, C. Articles by Chopineau, M. PubMed PubMed Citation Articles by Galet, C. Articles by Chopineau, M.

Department of Pharmacology, Roy J and Lucille A Carver College of Medicine, The University of Iowa, 2-319B BSB, 51 Newton Road, Iowa City, Iowa 52242-1109, USA
¹ Laboratoire de Physiologie de la Reproduction et des Comportements, UMR 6175 INRA-CNRS-Université François Rabelais de Tours-Haras Nationaux, 37380 Nouzilly, France

(Correspondence should be addressed to M Chopineau; Email: chopinea{at}tours.inra.fr)

The dual LH and FSH activity of the equine LH (eLH)/equine chorionic gonadotropin (eCG) in heterologous species makes eLH/CG a good model to study structure/function relationships of gonadotropins. In order to bypass the problem of intracellular association of the heterodimer, a recombinant single-chain βeLH/CG was used to identify sequences in the β-subunit involved in the secretion and activities of the hormone. The C-terminal region of the β-subunit was progressively truncated. All resulting truncated single-chains were secreted in the media as detected by an anti-βpeptide antibody in reducing conditions. However, using a conformation sensitive ELISA we show that the truncated single-chains were differently recognized: deletion of the last 40 amino acids of the β-subunit (β109eLH/CG) resulted in a 90% decrease in the recognized correctly folded hormone compared with the full-length βeLH/CG single-chain and no properly folded hormone was detected in the secretion medium when the last 46 amino acids of the β-subunit were deleted (β103eLH/CG). We thus focused on the six amino acids sequence 104–109, which belongs to the seat-belt region. Mutation of the 104–109 sequence in alanines in the full-length βeLH/CG (β104–109Ala) led to a 50% decrease in the production of properly folded hormone in COS-7 as well as in T3 pituitary cells. Moreover, the FSH activity of this mutant was decreased by 70% whereas its LH activity remained intact. These data lead us to conclude that the 104–109 region of the β eLH/CG subunit is essential for the secretion of a fully folded βeLH/CG and for its FSH activity but not for its LH activity.