GALECTIN-8 - A NEW RAT LECTIN, RELATED TO GALECTIN-4
GALECTIN-8 - A NEW RAT LECTIN, RELATED TO GALECTIN-4
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DOI：
10.1074/jbc.270.7.3447
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发表时间：
1995-02-17
影响因子：
4.8
通讯作者：
ZICK, Y
中科院分区：
文献类型：
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作者：
HADARI, YR;PAZ, K;ZICK, Y
从大鼠肝脏cDNA表达文库中克隆了一个具有凝集素（s型凝集素）特征的35 kDa蛋白。由于已经有了半乳糖凝集素1-7的名称，这种新蛋白被命名为半乳糖凝集素-8。有三种证据表明半乳糖凝集素-8确实是一种新型的半乳糖凝集素：(1)其推导出的氨基酸序列包含两个与半乳糖凝集素碳水化合物结合有关的保守基序结构域；(2)半乳糖凝集素-8 cDNA的体外翻译产物或细菌表达的重组半乳糖凝集素-8具有生物活性，具有糖结合和血凝活性。（iii）一种预期大小的蛋白（34 kDa），与乳糖- sepharose结合，并与半乳糖凝集素-8特异性抗体反应，存在于大鼠肝脏中，占Triton x -100可溶性肝蛋白总量的0.025%。总的来说，半乳糖凝集素-8在结构上与半乳糖凝集素-4相关（34%的同一性），半乳糖凝集素-4是一种可溶性的大鼠半乳糖凝集素，在同一多肽链中有两个碳水化合物结合结构域，由一个连接肽连接。尽管如此，有几个重要的特征将这两种半乳糖凝集素区分开来：(i) Northern blot分析显示，半乳糖凝集素-8不同于半乳糖凝集素-4局限于肠和胃，半乳糖凝集素-8在肝、肾、心肌、肺和脑中表达；（ii）与半乳糖凝集素-4不同，但与半乳糖凝集素-1和-2相似，半乳糖凝集素-8含有4个胱氨酸残基；（iii）半乳糖凝集素-8的连接肽是独特的，与任何已知的蛋白质没有相似性；（iv）半乳糖凝集素-8的n端碳水化合物结合区含有一个独特的WG-E-I基序，而不是普遍认为的在所有半乳糖凝集素的糖结合中起重要作用的WG-E-R/K基序。因此，与半乳糖凝集素-4一起，半乳糖凝集素-8代表了一个半乳糖凝集素亚家族，由单个多肽链中结构不同的碳水化合物识别域的串联重复组成。
A protein of 35 kDa which has the characteristic properties of galectins (S-type lectins) was cloned from rat liver cDNA expression library. Since names for galectins 1-7 were already assigned, this new protein was named galectin-8. Three lines of evidence demonstrate that galectin-8 is indeed a novel galectin: (i) its deduced amino acid sequence contains two domains with conserved motifs that are implicated in the carbohydrate binding of galectins, (ii) in vitro translation products of galectin-8 cDNA or bacterially expressed recombinant galectin-8 are biologically active and possess sugar binding and hemagglutination activity, and (iii) a protein of the expected size (34 kDa) that binds to lactosyl-Sepharose and reacts with galectin-8-specific antibodies is present in rat liver and comprises similar to 0.025% of the total Triton X-100-soluble hepatic proteins. Overall, galectin-8 is structurally related (34% identity) to galectin-4, a soluble rat galectin with two carbohydrate-binding domains in the same polypeptide chain, joined by a link peptide. Nonetheless, several important features distinguish these two galectins: (i) Northern blot analysis revealed that, unlike galectin-4 that is confined to the intestine and stomach, galectin-8 is expressed in liver, kidney, cardiac muscle, lung, and brain; (ii) unlike galectin-4, but similar to galectins-1 and -2, galectin-8 contains 4 Cys residues; (iii) the link peptide of galectin-8 is unique and bears no similarity to any known protein; (iv) the N-terminal carbohydrate-binding region of galectin-8 contains a unique WG-E-I motif instead of the consensus WG-E-R/K motif implicated as playing an essential role in sugar-binding of all galectins. Together with galectin-4, galectin-8 therefore represents a subfamily of galectins consisting of a tandem repeat of structurally different carbohydrate recognition domains within a single polypeptide chain.