Abstract
BackgroundThe Escherichia coli uropathogenic-specific protein (Usp) is a bacteriocin-like genotoxin, active against mammalian cells and associated with E. coli strains that provoke pyelonephritis, prostatitis and bacteraemia. Usp is encoded by a small pathogenicity island with three downstream small open reading frames (Imu1-3) that are believed to provide immunity to the producer. To prevent host suicide, colicins, bacteriocins of E. coli, form tight complexes with their cognate immunity proteins. Colicin – immunity protein complexes are among the strongest protein complexes known. Here, the Usp associated immunity protein 3 (Imu3) was partially characterized to gain insight into its role and mechanism of activity.ResultsIsolation and partial characterisation of the Usp-associated immunity protein-3 (Imu3) revealed that, while Usp and Imu3 do not form a high affinity complex, Imu3 exhibits DNA and RNA binding activity. Imu3 was also shown to protect DNA against degradation by colicin E7.ConclusionsOur data infer that nonspecific DNA binding of the Imu3 immunity protein, prevents suicide of E. coli producing the genotoxin Usp.
Highlights
The Escherichia coli uropathogenic-specific protein (Usp) is a bacteriocin-like genotoxin, active against mammalian cells and associated with E. coli strains that provoke pyelonephritis, prostatitis and bacteraemia
As protection of the Usp-producing bacterial cell might be provided by a mechanism that is different from that of the colicins, we have investigated the E. coli Usp-associated immunity protein immunity protein 3 (Imu3), previously designated OrfU3
It has been shown that colicin E7 and its immunity protein form a highaffinity complex [11], we were not able to confirm the formation of a high affinity complex between Usp and any of the three smaller proteins encoded downstream of the usp gene which were previously proposed to protect the Usp-producing cell against its endonucleolytic activity [5]
Summary
The Escherichia coli uropathogenic-specific protein (Usp) is a bacteriocin-like genotoxin, active against mammalian cells and associated with E. coli strains that provoke pyelonephritis, prostatitis and bacteraemia. The Escherichia coli uropathogenic-specific protein (Usp) has been shown to be associated with E. coli strains that provoke pyelonephritis, prostatitis and bacteraemia, and with increased virulence and fitness of pathogenic strains of E. coli [1,2,3,4]. Nucleotide sequence analysis has shown approximately 45% sequence identity of the Usp C-terminal region with that of the E. coli bacteriocin colicin E7, which has nuclease activity, while the Usp N-terminal region is similar to the Type VI protein secretion system component (Hcp like) [5,6,7]. Our study indicates that Imu has protective non specific DNA-binding abilities that could have possible biotechnological potential
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