Cattini-Schultz S V, Stanton P G, Robertson D M, Hearn M T
Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria, Australia.
Pept Res. 1995 Jul-Aug;8(4):214-26.
The role of specific amino acid residues within the sequence region between Leu26 and Thr46 of the human follicle-stimulating hormone (hFSH) alpha-subunit in the FSH-receptor interaction has been investigated. Competitive binding activities of seven sets of synthetic peptides were evaluated with both FSH- and luteinizing hormone (LH)-radioreceptor assay procedures. Set 1 included two overlapping peptides (alpha 25-41 and alpha 31-45) spanning the alpha 26-46 region, while Sets 2-6 included peptides of different size or structure in which the alpha 26-46 sequence was (i) sequentially truncated either from the N-terminus or from the C-terminus or both; (ii) alternatively reduced to a series of overlapping 13-mer peptides; or (iii) modified at the C-terminal Arg and Lys residues with substitution by Ala residues. In Set 7, synthetic peptides related to the parent alpha 26-46 peptide were prepared in which all the cysteine residues were substituted either singly or multiply with serine residues (i.e., alpha 26-46 Cys28,31,32-->Ser28,31,32). The ED50 values of the parent alpha 26-46 peptide in the FSH-radioreceptor assay were 2 and 7 x 10(-5) M, depending on whether the C-terminus was present as the amide or the free acid form, respectively. The substituted peptide alpha 26-46 (Cys28,31,32-->Ser28,31,32) was totally inactive in the FSH-radioreceptor assay. The truncation studies indicated that Cys28, Cys31 and Cys32 all contribute to the hormone-receptor interaction, with Cys32 being the major contributory cysteine residue. Similar results were observed when these peptides were evaluated in the LH-radioreceptor assay where the ED50 value for the parent alpha 26-46 peptide was observed to be 2 or 3 x 10(-5) M, depending on whether the C-terminus was the amide or the free acid. The Cys31 residue did not appear to contribute to the LH-receptor interaction; however, removal of Cys28 and Cys32 resulted in significant decreases in binding activity. The C-terminal truncation studies of the alpha 26-46 peptide revealed that Lys44 contributes to FSH receptor binding activity but does not contribute to the LH-receptor interaction. Truncation of the Arg42 residue or substitution of Arg42 with alanine in the alpha 31-45 peptide sequence prepared as part of the Set 1 synthetic peptides (i.e., the alpha 31-45 Arg42-->Ala42 peptide) or as part of the Set 6 peptide series, alpha 26-46 Arg42-->Ala42, confirmed the involvement of this residue in the LH-receptor interaction.(ABSTRACT TRUNCATED AT 400 WORDS)
已对人促卵泡激素（hFSH）α亚基Leu26和Thr46之间序列区域内特定氨基酸残基在FSH受体相互作用中的作用进行了研究。使用FSH和促黄体生成素（LH）放射受体测定程序评估了七组合成肽的竞争性结合活性。第1组包括两条跨越α26 - 46区域的重叠肽（α25 - 41和α31 - 45），而第2 - 6组包括不同大小或结构的肽，其中α26 - 46序列：（i）从N端或C端或两端依次截短；（ii）交替缩减为一系列重叠的13肽；或（iii）C端的Arg和Lys残基被Ala残基取代。在第7组中，制备了与亲本α26 - 46肽相关的合成肽，其中所有半胱氨酸残基被丝氨酸残基单取代或多取代（即α26 - 46 Cys28,31,32→Ser28,31,32）。在FSH放射受体测定中，亲本α26 - 46肽的ED50值分别为2×10⁻⁵ M和7×10⁻⁵ M，这取决于C端是以酰胺形式还是游离酸形式存在。取代肽α26 - 46（Cys28,31,32→Ser28,31,32）在FSH放射受体测定中完全无活性。截短研究表明，Cys28、Cys31和Cys32均对激素 - 受体相互作用有贡献，其中Cys32是主要的半胱氨酸贡献残基。当在LH放射受体测定中评估这些肽时，观察到了类似结果，其中亲本α26 - 46肽的ED50值为2×10⁻⁵ M或3×10⁻⁵ M，这取决于C端是酰胺还是游离酸。Cys31残基似乎对LH受体相互作用无贡献；然而，去除Cys28和Cys32会导致结合活性显著降低。α26 - 46肽的C端截短研究表明，Lys44对FSH受体结合活性有贡献，但对LH受体相互作用无贡献。作为第1组合成肽（即α31 - 45 Arg42→Ala42肽）的一部分或作为第6组肽系列α26 - 46 Arg42→Ala42制备的α31 - 45肽序列中Arg42残基的截短或用丙氨酸取代Arg42，证实了该残基参与LH受体相互作用。（摘要截断于400字）
