Solid-Phase Synthesis and Evaluation of Glycopeptide Fragments from Rat Epididymal Cysteine-Rich Secretory Protein-1 (Crisp-1) ‡
作者:Mian Liu、David W. Hamilton、George Barany
DOI:10.3390/molecules15096399
日期:——
Three 18-residue peptides with the sequence Glp-Asp-Thr-Thr-Asp-Glu-Trp-Asp-Arg-Asp-Leu-Glu-Asn-Leu-Ser-Thr-Thr-Lys, taken from the N-terminus of the rat epididymal cysteine-rich secretory protein (Crisp-1) that is important in the fertilization process, were prepared by Fmoc solid-phase synthesis using a convergent strategy. These peptides were the parent sequence, plus two possible α-O-linked TN antigen-containing glycopeptides with a Thr(α-D-GalNAc) residue in place of either Thr3 or Thr4. During chain assembly, two deletion peptides [des-Asp2 and des-Thr(Ac3-α-D-GalNAc)] and one terminated peptide [N-acetylated 14-mer] arose, as did several peptides in which aspartimide formation had occurred at each of the four possible positions in the sequence. These by-products totaled ~20% of the desired product; they were recognized by HPLC and ESI-MS and removed during the intermediate purifications. Final products, obtained in 15-21% overall yields, were characterized by HPLC purities and ESI-MS. Circular dichroism (CD) spectra for all three purified peptides, recorded in pure water and in trifluoroethanol-H2O (1:1), revealed that the presence of a sugar moiety does not significantly impact the sampled conformations. Future biological evaluation could elucidate the nature and locus of sugar modification of Crisp-1, and provide insight as to why Crisp-1 protein E binds sperm irreversibly, in contrast to protein D that lacks a sugar near the N-terminus and only binds sperm loosely.
三个 18 残基肽,其序列为 Glp-Asp-Thr-Thr-Asp-Glu-Trp-Asp-Arg-Asp-Leu-Glu-Asn-Leu-Ser-Thr-Thr-Lys,取自 N 末端使用收敛策略通过 Fmoc 固相合成制备了在受精过程中重要的大鼠附睾富含半胱氨酸的分泌蛋白 (Crisp-1)。这些肽是母体序列,加上两个可能的含α-O-连接的TN抗原的糖肽,其中Thr(α-D-GalNAc)残基代替了Thr3或Thr4。在链组装过程中,出现了两种缺失肽 [des-Asp2 和 des-Thr(Ac3-α-D-GalNAc)] 和一种终止肽 [N-乙酰化 14 聚体],以及在其中发生天冬酰亚胺形成的几种肽。序列中四个可能位置中的每一个。这些副产品总计约占所需产品的 20%;它们被 HPLC 和 ESI-MS 识别并在中间纯化过程中被去除。最终产物的总产率为 15-21%,并通过 HPLC 纯度和 ESI-MS 进行了表征。在纯水和三氟乙醇-H2O (1:1) 中记录的所有三种纯化肽的圆二色性 (CD) 光谱表明,糖部分的存在不会显着影响采样的构象。未来的生物学评估可以阐明 Crisp-1 糖修饰的性质和位点,并深入了解为什么 Crisp-1 蛋白 E 不可逆地结合精子,而蛋白 D 则在 N 末端附近缺乏糖,仅结合精子松散地。