广州桑树矮缩病植原体secE基因序列分析与蛋白结构预测

Analysis of secE Gene Sequence from Phytoplasma Associated with Mulberry Dwarf Disease in Guangzhou and Prediction of its Protein Structure

[目的]预测广州桑树矮缩病植原体secE蛋白的抗原性。[方法]应用PCR技术从典型矮缩症状的桑树植株总DNA中扩增到约400 bp的特异片段,将此片段克隆后与GeneBank中已报道的5种植原体的secE基因进行序列同源性分析,并对克隆基因所编码的蛋白进行理化性质、二级结构、跨膜区以及前导信号序列分析。[结果]该片段长411 bp,编码136个氨基酸的蛋白。桑树矮缩植原体与洋葱黄化植原体同源性最高,核苷酸和编码的氨基酸序列同源率分别为100%和99%。secE蛋白理化性质预测其理论等电点为9.33;二级结构主要为螺旋,其次为折叠和无规则卷曲,无转角;有3个明显的疏水区,易形成跨膜螺旋;有4个明显的抗原区域。[结论]该secE蛋白具有良好的抗原性。

[Objective]The aim was to predict the antigenicity of secE protein from phytoplasma associated with mulberry dwarf disease in Guangzhou.[Method]A fragment about 400bp was amplified by polymerase chain reaction from the total DNA of infected mulberry plants with typical dwarf symptom.The fragment was cloned followed by nucleotide acid sequence analysis with other 5 phytoplasmas of GenBank available.The analysis of physiochemical property,secondary structure,transmembrane domains and preamble signal sequence of protein encoded by cloned gene were made as well.[Result]The fragment was 411 bp in length,encoding a predicted protein of 136 amino acids.Homology analysis of sequence showed that MD-guangzhou phytoplasma was almost identical to OY-M phytoplasma.Homology rates of secE gene and coded amino acid sequence were 100% and 99% respectively.The physical and chemical properties analysis of protein encoded by secE predicted that isoelectric point was 9.33.Their secondary structure was mainly helix,secondly sheet and coil,but no turn.The secE protein possesed three evident hydrophobic regions which could form transmembrane helix easily and four evident antigenicity regions.[Conclusion]The secE portein should be of good antigenicity.