Department of Biophysics, All India Institute of Medical Sciences, New Delhi, India.
Int J Biol Macromol. 2012 Mar 1;50(2):317-22. doi: 10.1016/j.ijbiomac.2011.12.015. Epub 2011 Dec 23.
Prolactin inducible protein (PIP) is a 17 kDa glycoprotein. It binds to many proteins including fibrinogen, actin, keratin, myosin, immunoglobulin G, CD4, and human zinc-alpha-2 glycoprotein. Its ability to bind a large array of proteins indicates its multifaceted role in various biological processes, such as fertility, immunoregulation, antimicrobial activity, apoptosis, and tumor progression. Here, we present the first report of native human serum albumin (HSA)-PIP complex formation in seminal plasma. The complex was purified by chromatographic separation techniques, analyzed by gel electrophoresis, identified by MALDI-TOF mass spectrometry and validated by co-immunoprecipitation coupled with western blotting experiments. Moreover, the behavior of complex in solution was analyzed by dynamic light scattering and interacting residues were identified by in silico protein-protein docking. The purified protein complex shows two bands (67 kDa and 17 kDa) on SDS-PAGE gel and a single band (~85 kDa) on native PAGE gel. The predicted complex structure has 13 intermolecular hydrogen bonds, which may contribute to the overall stability of the complex. As HSA has been known to preserve the motility of sperm, native HSA-PIP complex formation may point towards an important role of PIP, which can directly be correlated with male fertility/infertility.
泌乳素诱导蛋白（PIP）是一种 17kDa 的糖蛋白。它可以与许多蛋白质结合，包括纤维蛋白原、肌动蛋白、角蛋白、肌球蛋白、免疫球蛋白 G、CD4 和人锌-α-2 糖蛋白。它能够与多种蛋白质结合，表明其在许多生物学过程中具有多方面的作用，如生育能力、免疫调节、抗菌活性、细胞凋亡和肿瘤进展。在这里，我们首次报道了天然人血清白蛋白（HSA）-PIP 复合物在精液中的形成。该复合物通过色谱分离技术进行纯化，通过凝胶电泳进行分析，通过 MALDI-TOF 质谱进行鉴定，并通过共免疫沉淀结合 Western blot 实验进行验证。此外，还通过动态光散射分析了复合物在溶液中的行为，并通过计算蛋白质-蛋白质对接鉴定了相互作用的残基。纯化的蛋白复合物在 SDS-PAGE 凝胶上显示出两条带（67kDa 和 17kDa），在 native PAGE 凝胶上显示出一条带（~85kDa）。预测的复合物结构有 13 个分子间氢键，这可能有助于复合物的整体稳定性。由于 HSA 已知可以保持精子的运动能力，因此天然 HSA-PIP 复合物的形成可能表明 PIP 具有重要作用，这与男性生育能力/不育直接相关。
