Liu J, Seul U, Thompson R
Max-Planck-Institut für Züchtungsforschung, Köln, Germany.
Plant Mol Biol. 1997 Jan;33(2):291-300. doi: 10.1023/a:1005746713759.
A pollen-specific cDNA was isolated from a cDNA library of in vitro germinated pollen of the diploid potato species Solanum berthaultii. The cDNA clone, designated SB401, hybridizes to a messenger RNA of 1.2 kb length in mature and germinated pollen. SB401 messenger RNA is absent from other parts of the plant, including other flower tissues. SB401 cDNA, which possesses a long stretch of AT-rich 5'-untranslated leader sequence, encodes a glutamic acid-rich protein (GARP) which is hydrophilic throughout and contains six imperfect repeated motifs of the sequence V-V-E-K-K-N/E-E with the di-basic amino acid residue pair (K-K) as the core within the repeats. These repeats are spaced at irregular intervals and predicted to form an alpha-helical structure. The SB401 protein was over-expressed in Escherichia coli and the purified protein was used for raising antiserum. Both E. coli-expressed and the endogenous SB401 proteins in pollen and pollen tubes appear much larger on SDS-polyacrylamide gels than their calculated molecular masses. Immunoblotting revealed the protein to be most abundant in germinated pollen. The structural features of SB401 protein and a possible role for the protein in pollen development, pollen germination, and pollen tube growth are discussed.
从二倍体马铃薯种伯氏马铃薯（Solanum berthaultii）体外萌发花粉的cDNA文库中分离出一个花粉特异性cDNA。该cDNA克隆命名为SB401，在成熟和萌发的花粉中与长度为1.2 kb的信使RNA杂交。植物的其他部分，包括其他花组织中不存在SB401信使RNA。SB401 cDNA具有一段很长的富含AT的5'-非翻译前导序列，编码一种富含谷氨酸的蛋白（GARP），该蛋白整体呈亲水性，包含六个不完美的重复基序V-V-E-K-K-N/E-E，重复序列中的核心是双碱性氨基酸残基对（K-K）。这些重复序列以不规则的间隔排列，预计会形成α-螺旋结构。SB401蛋白在大肠杆菌中过表达，纯化后的蛋白用于制备抗血清。在SDS-聚丙烯酰胺凝胶上，大肠杆菌表达的以及花粉和花粉管中的内源性SB401蛋白看起来都比其计算分子量要大得多。免疫印迹显示该蛋白在萌发的花粉中含量最高。本文讨论了SB401蛋白的结构特征以及该蛋白在花粉发育、花粉萌发和花粉管生长中的可能作用。
