Lamppa G K, Morelli G, Chua N H
Mol Cell Biol. 1985 Jun;5(6):1370-8. doi: 10.1128/mcb.5.6.1370-1378.1985.
A genomic clone for a major chlorophyll a/b-binding polypeptide of the light-harvesting complex has been sequenced from wheat. This gene, whAB1.6, encodes a 70-nucleotide 5'-nontranslated spacer, a 34-amino-acid NH2-terminal extension, i.e., the transit peptide, and a mature coding protein of 232 amino acid residues. The exact molecular weight of the precursor polypeptide is 28,560. The transit peptide is basic and is rich in serines. No intervening sequences are found in this gene. The transcription start site of the whAB1.6 gene occurs at AAAC as determined by S1 nuclease analysis. Putative regulatory sequences occur upstream of the gene at -25 (TTTAAATA) and at -72 (CCAACCA). Northern blots show a single RNA species estimated to be 1,100 nucleotides. Heterogeneity of the RNA population is demonstrated in S1 nuclease analyses with a 5'-end-labeled fragment that extends 191 nucleotides into the mature protein coding sequence. At least seven different transcripts can be recognized. The highest levels of RNA transcribed from the whAB1.6 gene are found in the basal segments of the wheat leaf, whereas other chlorophyll a/b-binding transcripts in the cell show a different pattern of abundance. As a control, we show that roots do not contain chlorophyll a/b-binding RNA. The most abundant RNA species shows an interrupted homology with the whAB1.6 gene at the start of the mature protein coding sequence; another species shows homology beginning at the start of the transit peptide and does not include the nontranslated region. Chlorophyll a/b-binding polypeptides accumulate toward the tip of the leaf as shown by Western blot analysis of total thylakoid proteins.
从小麦中已对光捕获复合体主要叶绿素a/b结合多肽的基因组克隆进行了测序。该基因whAB1.6编码一个70个核苷酸的5'非翻译间隔区、一个34个氨基酸的NH2末端延伸部分，即转运肽，以及一个由232个氨基酸残基组成的成熟编码蛋白。前体多肽的确切分子量为28,560。转运肽呈碱性且富含丝氨酸。该基因中未发现内含序列。通过S1核酸酶分析确定，whAB1.6基因的转录起始位点位于AAAC处。推测的调控序列出现在基因上游-25（TTTAAATA）和-72（CCAACCA）处。Northern印迹显示单一RNA种类，估计为1100个核苷酸。用一个5'末端标记的片段进行S1核酸酶分析，该片段延伸至成熟蛋白编码序列191个核苷酸处，证明了RNA群体的异质性。至少可以识别出七种不同的转录本。从whAB1.6基因转录的最高水平的RNA存在于小麦叶片的基部，而细胞中其他叶绿素a/b结合转录本显示出不同的丰度模式。作为对照，我们表明根中不含有叶绿素a/b结合RNA。最丰富的RNA种类在成熟蛋白编码序列起始处与whAB1.6基因有间断的同源性；另一种类在转运肽起始处开始显示同源性，且不包括非翻译区。通过对总类囊体蛋白的Western印迹分析表明，叶绿素a/b结合多肽在叶片尖端积累。
