Hoffman L M, Donaldson D D
EMBO J. 1985 Apr;4(4):883-9. doi: 10.1002/j.1460-2075.1985.tb03714.x.
A lambda 1059 library of Phaseolus vulgaris cv. 'Tendergreen' DNA was screened with a cloned lectin-like cDNA. Among the phages selected was clone lambda B10 containing two complete lectin genes in the same orientation approximately 4 kb apart. The DNA sequences of the lectin genes and their flanking regions have been determined and their transcriptional initiation sites were located by S1 nuclease mapping. On the basis of the deduced amino acid sequences and compositions and the mol. wts. of their encoded glycoproteins, the genes, dlec1 and dlec2, are predicted to encode erythro- and leucoagglutinating phytohemagglutinins (PHA-E and PHA-L), respectively. The mRNA coding regions of dlec1 and dlec2 are 90% homologous, suggesting an origin involving duplication of an ancestral gene. Both lectin genes are intronless and have at least two ATG codons in a short (11-14 bp) 5'-untranslated region. Most of their 5'-untranslated regions consist of alternating pyrimidines and purines (RY repeats). Upstream sequences are also highly conserved between dlec1 and dlec2, including stretches of nine or more alternating R and Y residues. RY repeats of such length are not found within the protein coding portion of dlec1, dlec2 or a Phaseolus lectinlike gene previously described. Overlapping double (dlec1) or triple (dlec2) polyadenylation addition signals are found and there is an unusually high degree of homology (84%) between their 3'-untranslated regions.(ABSTRACT TRUNCATED AT 250 WORDS)
用克隆的类凝集素cDNA筛选菜豆品种“嫩绿”的λ1059文库。在筛选出的噬菌体中,克隆λB10含有两个同向排列的完整凝集素基因,相距约4kb。已测定了凝集素基因及其侧翼区域的DNA序列,并通过S1核酸酶图谱定位了它们的转录起始位点。根据推导的氨基酸序列、组成以及其编码糖蛋白的分子量,预测基因dlec1和dlec2分别编码红细胞凝集和白细胞凝集植物血凝素(PHA - E和PHA - L)。dlec1和dlec2的mRNA编码区有90%的同源性,表明其起源涉及一个祖先基因的复制。两个凝集素基因都没有内含子,并且在短的(11 - 14bp)5'非翻译区至少有两个ATG密码子。它们的5'非翻译区大部分由嘧啶和嘌呤交替组成(RY重复)。dlec1和dlec2的上游序列也高度保守,包括九个或更多R和Y残基交替的片段。在dlec1、dlec2或先前描述的菜豆类凝集素基因的蛋白质编码部分未发现如此长度的RY重复。发现了重叠的双(dlec1)或三(dlec2)聚腺苷酸化添加信号,并且它们的3'非翻译区之间存在异常高的同源性(84%)。(摘要截断于250字)