Department of Plant Pathology, Nanjing Agricultural University, Nanjing, China.
J Microbiol Biotechnol. 2010 Jan;20(1):54-62.
A novel harpin-like protein, HpaXm, was described from cotton leaf blight bacteria, Xanthomonas. citri subsp. malvacearum. The hpaXm was found to be localized between hrp2 and hrcC. A phylogenetic analysis of the complete amino acid sequence or solely the 13 highly conserved residues H2N-SEKQLDQLLTQLI-COOH in the N-terminal alpha-helix indicates that HpaXm is evolutionarily closer to HpaGXag and HpaXac than to Hpa1Xoo and Hpa1Xoc. A synthesized peptide containing two heptads, 39-LDQLLTQ-LIMALLQ-52, from the N-terminal alpha-helical region of HpaXm displayed a comparable activity in inducing HR, but other two synthesized derivatives, HpaXmDeltaT44C and HpaXmDeltaM48Q showed a reduced activity of HR. The data from a GST trap test revealed that HpaXm was released into the extracellular medium, hpaXm mutant deficient for the leader peptide (1-MNSLNTQIGANSSFL-15) was unable to be secreted outside cells but still induced HR in tobacco leaves.
从棉花叶枯病菌，黄单胞菌属，柑橘亚种中描述了一种新型的 harpin 样蛋白 HpaXm。发现 hpaXm 定位于 hrp2 和 hrcC 之间。完整氨基酸序列或 N 端α螺旋中 13 个高度保守残基 H2N-SEKQLDQLLTQLI-COOH 的系统发育分析表明，HpaXm 与 HpaGXag 和 HpaXac 的进化关系比与 Hpa1Xoo 和 Hpa1Xoc 的进化关系更密切。从 HpaXm 的 N 端α螺旋区合成的含有两个七肽，39-LDQLLTQ-LIMALLQ-52 的肽显示出相当的诱导 HR 活性，但另外两个合成衍生物 HpaXmDeltaT44C 和 HpaXmDeltaM48Q 的 HR 活性降低。GST 捕获试验的数据表明 HpaXm 被释放到细胞外培养基中，缺乏前导肽（1-MNSLNTQIGANSSFL-15）的 hpaXm 突变体无法分泌到细胞外，但仍能在烟草叶片中诱导 HR。
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