TAILIEUCHUNG - A putative lytic transglycosylase tightly regulated and critical for the EHEC type three secretion

Abstract Open reading frame l0045 in the pathogenic island of enterohemorrhagic Escherichia coli O157:H7 has been predicted to encode a lytic transglycosylase that is homologous to two different gene products encoded by the same bacteria at loci away from the island. To deduce the necessity of the presence in the island, we created an l0045-deleted strain of EHEC and observed that both the level of cytosolic EspA and that of the other type III secreted proteins in the media were affected. In a complementation assay, a low level-expressing L0045 appeared to recover efficiently the type III secretion (TTS). On the. | Yu et al. Journal of Biomedical Science 2010 17 52 http content 17 1 52 a NSC The cost of publication In Journal of Blomodlcal Science Is bome by the National Science Council Taiwan JOURNAL OF BIOMEDICAL SCIENCE RESEARCH Open Access A putative lytic transglycosylase tightly regulated and critical for the EHEC type three secretion Yen-Chi Yu 1 Ching-Nan Lin 1 Shao-Hung Wang2 Swee-Chuan Ng 1 Wensi S Hu3 and Wan-Jr Syu 1 Abstract Open reading frame 10045 in the pathogenic island of enterohemorrhagic Escherichia coli O157 H7 has been predicted to encode a lytic transglycosylase that is homologous to two different gene products encoded by the same bacteria at loci away from the island. To deduce the necessity of the presence in the island we created an 10045-deleted strain of EHEC and observed that both the level of cytosolic EspA and that of the other type III secreted proteins in the media were affected. In a complementation assay a low level-expressing L0045 appeared to recover efficiently the type III secretion TTS . On the other hand when 10045 was driven to express robustly the intracellular levels of representative TTS proteins were severely suppressed. This suppression is apparently caused by the protein of L0045 per se since introducing an early translational termination codon abolished the suppression. Intriguingly the authentic L0045 was hardly detected in all lysates of EHEC differently prepared while the same construct was expectedly expressed in the K-12 strain. A unique network must exist in EHEC to tightly regulate the presence of L0045 and we found that a LEE regulator GrlA is critically involved in this regulation. Introduction Enterohemorrhagic E. coli EHEC causes bloody diarrhea and forms typical histological lesions called attaching and effacing A E lesions in the infected intestinal tract. This pathogenic characteristic has been attributed to that the bacteria attach to the epithelial cells and employ a type III secretion system

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