Goulart Carolina L, Lery Letícia M S, Diniz Michelle M P, Vianez-Junior João L, Neves-Ferreira Ana Gisele C, Perales Jonas, Bisch Paulo M, von Krüger Wanda M A
Unidade Multidisciplinar de Genômica, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil.
FEMS Microbiol Lett. 2009 Sep;298(2):241-8. doi: 10.1111/j.1574-6968.2009.01727.x. Epub 2009 Jul 13.
The PhoB/PhoR-dependent response to inorganic phosphate (Pi)-starvation in Vibrio cholerae O1 includes the expression of vc0719 for the response regulator PhoB, vca0033 for an alkaline phosphatase and vca1008 for an outer membrane protein (OMP). Sequences with high identity to these genes have been found in the genome of clinical and environmental strains, suggesting that the Pi-starvation response in V. cholerae is well conserved. VCA1008, an uncharacterized OMP involved in V. cholerae pathogenicity, presents sequence similarity to porins of Gram-negative bacteria such as phosphoporin PhoE from Escherichia coli. A three-dimensional model shows that VCA1008 is a 16-stranded pore-forming beta-barrel protein that shares three of the four conserved lysine residues responsible for PhoE anionic specificity with PhoE. VCA1008 beta-barrel apparently forms trimers that collapse into monomers by heating. Properties such as heat modifiability and resistance to denaturation by sodium dodecyl sulfate at lower temperatures permitted us to suggest that VCA1008 is a classical porin, more precisely, a phosphoporin due to its Pi starvation-induced PhoB-dependent expression, demonstrated by electrophoretic mobility shift assay and promoter fusion-lacZ assays.
霍乱弧菌O1中PhoB/PhoR依赖的对无机磷酸盐（Pi）饥饿的应答包括：应答调节因子PhoB的vc0719、碱性磷酸酶的vca0033以及外膜蛋白（OMP）的vca1008的表达。在临床和环境菌株的基因组中发现了与这些基因具有高度同源性的序列，这表明霍乱弧菌中的Pi饥饿应答是高度保守的。VCA1008是一种参与霍乱弧菌致病性的未表征的OMP，与革兰氏阴性菌的孔蛋白具有序列相似性，如大肠杆菌的磷酸孔蛋白PhoE。三维模型显示，VCA1008是一种由16条链组成的形成孔道的β桶蛋白，与PhoE共享负责PhoE阴离子特异性的四个保守赖氨酸残基中的三个。VCA1008β桶显然形成三聚体，通过加热会解聚为单体。热可修饰性以及在较低温度下对十二烷基硫酸钠变性的抗性等特性使我们认为，VCA1008是一种经典孔蛋白，更确切地说，是一种磷酸孔蛋白，因为其Pi饥饿诱导的PhoB依赖表达已通过电泳迁移率变动分析和启动子融合 - lacZ分析得到证实。
