Follitropin Conformational Stability Mediated by Loop 2 Effects Follitropin-Receptor Interaction
详细信息 查看全文
- 作者：Karen E. Roth and and James A. Dias
- 刊名：Biochemistry
- 出版年：1996
- 出版时间：June 18, 1996
- 年：1996
- 卷：35
- 期：24
- 页码：7928 - 7935
- 全文大小：379K
- 年卷期：v.35,no.24(June 18, 1996)
- ISSN：1520-4995
文摘
Follicle-stimulating hormone (FSH) is in the family ofpituitary/placental glycoprotein hormoneswhich also includes luteinizing hormone (LH), chorionic gonadotropin(hCG), and thyroid-stimulatinghormone. These hormones are heterodimers composed of common 
-and similar but unique 
-subunits.The 21 amino acid loop between Y33 and F53 of the FSH -subunit(L2) can be switched into L2 ofhCG without a loss of receptor binding, yet mutation of hFSH37LVY39 to37AAA39 was antecedent toa 20-fold reduction in receptor binding (based on ID50).A mutation in the LH gene, which causes Q54to be R, causes hypogonadism. This residue is conserved in theglycoprotein hormones and correspondsto Q48 in hFSH. Mutation of hFSH48QKTCT52 to48AAACA52 resulted in a failure ofheterodimerformation. In the current study single mutations were made topinpoint which of the seven hFSH residuesin the 37LVY39 to37AAA39 and the48QKTCT52 to48AAACA52 mutants were responsible for theobservedphenotypes. A single mutation of T52 to alanine was sufficient tocause a reduction in expression ofheterodimeric hormone. Single mutants Q48A, T50A, V38A, Y39A, and,to a lesser extent, T52A formedheterodimer. However, these hFSH mutants were markedly unstable atpH 2.0. Thus, acid dissociationcan be used to reveal metastable forms of this protein. MutanthFSH Q48A was also 8-fold less activethan wild-type hFSH when assayed for binding to hFSH receptors.hFSH V38A and Y39A mutantsaffected receptor binding; however, neither mutation alone causedgreater than a 2-fold decrease in receptorbinding activity. In summary, these results identify singleimportant residues in the long loop (betweenY33 and F53) of the hFSH -subunit which are required for propersubunit interactions that provideconformational stability which in turn is necessary for FSH-receptorinteraction.
-and similar but unique -subunits.The 21 amino acid loop between Y33 and F53 of the FSH -subunit(L2) can be switched into L2 ofhCG without a loss of receptor binding, yet mutation of hFSH37LVY39 to37AAA39 was antecedent toa 20-fold reduction in receptor binding (based on ID50).A mutation in the LH gene, which causes Q54to be R, causes hypogonadism. This residue is conserved in theglycoprotein hormones and correspondsto Q48 in hFSH. Mutation of hFSH48QKTCT52 to48AAACA52 resulted in a failure ofheterodimerformation. In the current study single mutations were made topinpoint which of the seven hFSH residuesin the 37LVY39 to37AAA39 and the48QKTCT52 to48AAACA52 mutants were responsible for theobservedphenotypes. A single mutation of T52 to alanine was sufficient tocause a reduction in expression ofheterodimeric hormone. Single mutants Q48A, T50A, V38A, Y39A, and,to a lesser extent, T52A formedheterodimer. However, these hFSH mutants were markedly unstable atpH 2.0. Thus, acid dissociationcan be used to reveal metastable forms of this protein. MutanthFSH Q48A was also 8-fold less activethan wild-type hFSH when assayed for binding to hFSH receptors.hFSH V38A and Y39A mutantsaffected receptor binding; however, neither mutation alone causedgreater than a 2-fold decrease in receptorbinding activity. In summary, these results identify singleimportant residues in the long loop (betweenY33 and F53) of the hFSH -subunit which are required for propersubunit interactions that provideconformational stability which in turn is necessary for FSH-receptorinteraction.