Regulators of Escherichia coli K99 region 1 genes

Advances in Experimental Medicine and Biology
T Lo-TsengR E Isaacson

Abstract

Expression of K99 is highly regulated being dependent on 8 K99-specific genes and several host-specific genes including cyclic AMP receptor protein (Crp) and leucine responsive protein (Lrp). The 8 K99-specific genes are organized into 3 separately regulated clusters (regions I-III) with region I and II genes being dependent on Crp. Using TnphoA tagged K99 genes, Lrp was shown to be required for expression of region I genes. Differential methylation of GATC boxes is a common method by which Lrp functions as a regulator. Two GATC boxes are present adjacent to the 5' end of fanA, the first gene. Using the restriction enzymes Dpn I and Mbo I which recognize methylated and non-methylated GATC boxes, respectively, it was shown that differential methylation was not a mechanism regulating K99 expression. Using a gel mobility shift assay and protein extracts from various strains, it was shown that a 625 bp DNA fragment adjacent to the 5' end of fanA bound protein prepared from Lrp+ strains but not from Lrp- strains. While region I genes also require CRP for expression, the same degree of gel shift was observed when the extract was prepared from a Crp- strain. The products of fanA and fanB are believed to be positive regulators. However...Continue Reading

Citations

Jan 11, 2011·Journal of Bacteriology·Shirley M EspertGeorge P Munson
Aug 26, 1998·Trends in Microbiology·R A Edwards, J L Puente

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