Yu Suhong, Chen Xinhua, Ao Jingqun
School of Life Sciences, Xiamen University, Xiamen, People's Republic of China.
Mol Biol Rep. 2009 Sep;36(7):1715-23. doi: 10.1007/s11033-008-9373-6. Epub 2008 Oct 14.
Beta(2)-microglobulin (beta(2)m), a protein necessary for proper folding, peptide binding, and surface display of class I antigens plays an important role in immune response. The full-length cDNA containing beta(2)m was cloned from the spleen cDNA library of large yellow croaker Pseudosciaena crocea (Pscr-beta ( 2 ) m) by expressed sequence tag (EST) analysis. The Pscr-beta ( 2 ) m is 926 nucleotides (nt) long, including an open reading frame (ORF) of 348 nt encoding a polypeptide of 116 amino acids (aa). The deduced Pscr-beta ( 2 ) m possessed all characteristic domains of beta(2)m in other species, including a 16-aa leader peptide and a typical immunoglobulin (Ig) and major histocompatibility complex protein (MHC) signature YSCRVTH at residues 81-87. Homology modeling showed that the 3D structure of Pscr-beta ( 2 ) m protein is similar to that of human beta(2)m, except for a beta-strand (G) being lost in Pscr-beta ( 2 ) m due to amino acid deletion (positions 94-95). Tissue expression profile analysis revealed that the Pscr-beta ( 2 ) m was constitutively expressed in all tissues examined, such as kidney, spleen, liver, gills, heart, intestine, brain, and muscle, although at different levels. Upon stimulation with poly(I:C) or inactivated trivalent bacterial vaccine, the expression of Pscr-beta ( 2 ) m was significantly up-regulated in intestine, kidney and spleen at 24 h post-induction, and increase of Pscr-beta ( 2 ) m transcripts was also observed in liver post-induction with poly(I:C). Real-time PCR further revealed that the expression of Pscr-beta ( 2 ) m in intestine, kidney and spleen tissues was differentially regulated by poly(I:C) and bacterial vaccine during 72 h of induction. These results suggested that Pscr-beta ( 2 ) m might be involved in both antiviral and antibacterial mechanisms in large yellow croaker.
β2-微球蛋白（β2m）是一种对I类抗原的正确折叠、肽结合和表面展示所必需的蛋白质，在免疫反应中起重要作用。通过表达序列标签（EST）分析，从大黄鱼（Pseudosciaena crocea）脾脏cDNA文库中克隆了包含β2m的全长cDNA（Pscr-β2m）。Pscr-β2m长926个核苷酸（nt），包括一个348 nt的开放阅读框（ORF），编码一个116个氨基酸（aa）的多肽。推导的Pscr-β2m具有其他物种β2m的所有特征结构域，包括一个16个氨基酸的前导肽以及在81-87位残基处的典型免疫球蛋白（Ig）和主要组织相容性复合体蛋白（MHC）特征序列YSCRVTH。同源建模显示，Pscr-β2m蛋白的三维结构与人β2m相似，只是由于氨基酸缺失（94-95位），Pscr-β2m中一条β链（G）缺失。组织表达谱分析显示，Pscr-β2m在所有检测组织如肾脏、脾脏、肝脏、鳃、心脏、肠道、大脑和肌肉中组成性表达，尽管表达水平不同。用聚肌胞苷酸（poly(I:C)）或灭活的三价细菌疫苗刺激后，诱导后24小时，Pscr-β2m在肠道、肾脏和脾脏中的表达显著上调，聚肌胞苷酸诱导后肝脏中也观察到Pscr-β2m转录本增加。实时PCR进一步显示，在诱导的72小时内，聚肌胞苷酸和细菌疫苗对肠道、肾脏和脾脏组织中Pscr-β2m的表达有不同的调节作用。这些结果表明，Pscr-β2m可能参与大黄鱼的抗病毒和抗菌机制。
