Heikinheimo R, Flego D, Pirhonen M, Karlsson M B, Eriksson A, Mäe A, Kõiv V, Palva E T
Department of Molecular Genetics, Uppsala Genetic Center, Swedish University of Agricultural Sciences.
Mol Plant Microbe Interact. 1995 Mar-Apr;8(2):207-17. doi: 10.1094/mpmi-8-0207.
The pectate lyase (Pel, EC 4.2.2.2) isoenzyme profile of Erwinia carotovora subsp. carotovora was characterized by isoelectric focusing, and the corresponding genes coding for four different exported Pels were cloned. The nucleotide sequence of the pelB gene encoding one of these isoenzymes was determined and was shown to contain 1,040-bp open reading frame coding for a 37,482-Da protein with a putative cleavable amino terminal signal peptide. Overexpression and selective labeling experiments with the pelB clone demonstrated the synthesis of a 35-kDa polypeptide, which is in accordance with the deduced size of the processed PelB. The predicted amino acid sequence of PelB was very similar to that of Pel-3 of another E.c. subsp. carotovora strain 71, but showed no similarity to other previously characterized pectinolytic enzymes. The pelB gene is located next to the previously characterized pehA gene encoding an endopolygalacturonase. The two genes are divergently transcribed from a common control region and are subject to similar global regulation by the central virulence regulator expI. Inactivation of pelB did not appear to reduce the virulence of the mutant strain, suggesting that pelB does not have a major role in pathogenicity. Unlike other Pels, PelB required partially methyl esterified pectin as substrate suggesting that PelB represents a novel isoform of pectate lyase.
通过等电聚焦对胡萝卜软腐欧文氏菌胡萝卜软腐亚种的果胶酸裂解酶（Pel，EC 4.2.2.2）同工酶谱进行了表征，并克隆了编码四种不同分泌型Pel的相应基因。测定了编码其中一种同工酶的pelB基因的核苷酸序列，结果表明该基因含有一个1040 bp的开放阅读框，编码一个37482 Da的蛋白质，该蛋白质带有一个假定的可裂解氨基末端信号肽。用pelB克隆进行的过表达和选择性标记实验表明合成了一种35 kDa的多肽，这与加工后的PelB的推导大小一致。PelB的预测氨基酸序列与另一株胡萝卜软腐欧文氏菌胡萝卜软腐亚种71的Pel-3非常相似，但与其他先前表征的果胶分解酶没有相似性。pelB基因位于先前表征的编码内切多聚半乳糖醛酸酶的pehA基因旁边。这两个基因从一个共同的控制区域反向转录，并受到中央毒力调节因子expI的类似全局调控。pelB的失活似乎并未降低突变菌株的毒力，这表明pelB在致病性中没有主要作用。与其他Pel不同，PelB需要部分甲基酯化的果胶作为底物，这表明PelB代表了一种新型的果胶酸裂解酶同工型。
