Kim D S, Rhew T H, Moss D J, Kim J Y
Department of Preventive Medicine and Industrial Medicine Research Institute, Dong-A University College of Medicine, Pusan, Korea.
Mol Cells. 1999 Jun 30;9(3):270-6.
GP55 is a family of glycoproteins distributed predominantly in the nervous system, and its previously characterized members, including the GP55A (EMBL Y08170) and E19S (EMBL Y08171) reveal a typical glycosyl phosphatidyl inositol (GPI)-anchored pattern for membrane proteins. CEPUS identified in this study appeared to represent the third member of GP55. This 3.2 kb long complete cDNA clone from the chicken brain exhibited 3 Ig-like domains. The open reading frame of CEPUS contains 313 amino acids, which can encode a 31.7 kDa core protein (pI 5.75) for the mature form. The signal peptide cleavage site was predicted at Gln25. The structural features of the CEPUS cDNA sequence represented a soluble counterpart to the recently identified cerebellar Purkinje cell specific antigen, CEPU-1. The sequence difference between CEPU-1 and CEPUS was only found in the C-terminus in which the CEPUS lacked the GPI-anchored binding site. It displays significant sequence homology to GP55-related molecules, including OBCAM, GP55A, E19S/LAMP, neurotrimin, and CEPU-1, which are all membrane attached types. The absence of the hydrophobic tail sequence in CEPUS may, therefore, suggest that CEPUS would represent the first identified secreted member in this group of genes. We defined that this molecule forms the opioid-binding cell adhesion molecule (OBCAM) subfamily in the molecular phylogeny. Structurally, these molecules represent acidic proteins (pI 5.47-6.09). Six cysteins, as well as 5 Asn-linked potential glycosylation sites were evolutionary-conserved, suggesting that this OBCAM subfamily resembles immunoglobulin-like and highly glycosylated molecules. The presence of CEPUS would probably suggest to us that the spatial/local expression of the CEPU gene may provide a favorable route for migrating CEPU-positive population of neurons to generate a neuron-specific guidance in developing neurons in vivo.
GP55是一类主要分布于神经系统的糖蛋白家族，其先前已被鉴定的成员，包括GP55A（EMBL Y08170）和E19S（EMBL Y08171），显示出膜蛋白典型的糖基磷脂酰肌醇（GPI）锚定模式。本研究中鉴定出的CEPUS似乎代表了GP55的第三个成员。这个来自鸡脑的3.2 kb长的完整cDNA克隆具有3个免疫球蛋白样结构域。CEPUS的开放阅读框包含313个氨基酸，可编码一个31.7 kDa的成熟形式核心蛋白（pI 5.75）。信号肽切割位点预测在Gln25处。CEPUS cDNA序列的结构特征代表了最近鉴定出的小脑浦肯野细胞特异性抗原CEPU-1的可溶性对应物。CEPU-1和CEPUS之间的序列差异仅在C末端被发现，其中CEPUS缺乏GPI锚定结合位点。它与包括OBCAM、GP55A、E19S/LAMP、神经微蛋白和CEPU-1在内的GP55相关分子显示出显著的序列同源性，这些分子均为膜附着类型。因此，CEPUS中疏水尾序列的缺失可能表明CEPUS是该基因家族中首个被鉴定出的分泌型成员。我们在分子系统发育中定义该分子形成阿片样物质结合细胞粘附分子（OBCAM）亚家族。在结构上，这些分子代表酸性蛋白（pI 5.47 - 6.09）。六个半胱氨酸以及5个潜在的N-糖基化位点在进化上是保守的，这表明这个OBCAM亚家族类似于免疫球蛋白样且高度糖基化的分子。CEPUS的存在可能向我们表明，CEPU基因的空间/局部表达可能为迁移的CEPU阳性神经元群体提供一条有利途径，从而在体内发育中的神经元中产生神经元特异性导向。
