Structural study of TcaR and its complexes with multiple antibiotics from Staphylococcus epidermidis

Abstract

TcaR and IcaR are a weak and a strong negative regulator of transcription of the ica locus, respectively, and their presence prevents the poly-N-acetylglucosamine production and biofilm formation in Staphylococcus epidermidis. Although TcaR was shown to interact with the ica promoter, the precise binding region and the mechanism of interaction remained unclear. Here we present the 3D structure of TcaR in its apo form and in complex with salicylate as well as several aminoglycoside and β-lactam antibiotics. A comparison of the native and complex TcaR structures indicates that the mechanism of regulation involves a large conformational change in the DNA-binding lobe. Here, we deduced the consensus binding sequence of two [∼TTNNAA] hexamers embedded in a 16 bp sequence for a TcaR dimer. Six TcaR dimers bind specifically to three approximately 33 bp segments close to the IcaR binding region with varying affinities, and their repressor activity is directly interfered by salicylate and different classes of natural antimicrobial compounds. We also found in this study that the antimicrobial compounds we tested were shown not only to inhibit TcaR-DNA interaction but also to further induce biofilm formation in S. epidermidis in our in vivo assay. The results support a general mechanism for antibiotics in regulating TcaR-DNA interaction and thereby help understand the effect of antibiotic exposure on bacterial antibiotic resistance through biofilm formation.repressor | biofilm | DNA binding | multiple drug resistance | transcription regulation

Reduced Vancomycin Susceptibility in anIn VitroCatheter-Related Biofilm Model Correlates with Poor Therapeutic Outcomes in Experimental Endocarditis Due to Methicillin-Resistant Staphylococcus aureus

“…However, the exact mechanisms involved in enhancing biofilm formation upon exposure to sub-MIC VAN levels in non-Rsp strains are not well known. In contrast to Staphylococcus epidermidis, few studies have examined the effects of sub-MIC antibiotics on S. aureus biofilm formation (14,(41)(42)(43)(44). One recent study reported that sub-MIC VAN levels can enhance S. aureus cell lysis and extracellular DNA release and promote biofilm formation (14).…”

Bases moleculares de la infección asociada a implantes ortopédicos

“…El aumento de la formación de biopelícula también se ha visto en S. epidermidis a través del aumento de la producción de Pia. Los antimicrobianos formarían un complejo con TcaR (regulador de la transcripción del operon ica) el cual produciría el aumento de expresión 47 . En el locus homólogo de S. epidermidis, la regulación del ica ocurre a través de una inactivación reversible con la inserción de una secuencia (IS256) en 25 a 35% de las variantes 48 .…”

The MarR Family of Transcriptional Regulators - A Structural Perspective

“…Although the ligand binding sites in ST1710 and MTH313 are comparable, we have not found any conformational changes in ST1710 between the apo and ligand bound complexes, as observed in MTH313. Meanwhile, eight salicylate molecules are bound to Staphylococcus epidermidis of TcaR (Chang et al, 2010). Among these eight molecules, two are bound similarly to that with MTH313, while the other two were observed in the more shallow binding pocket in each monomer.…”

“…The remaining ligands are highly exposed to the solvent. TcaR has also been crystallized with four different antibiotics (ampicillin, kanamycin, methicillin and penicillin), revealing their interactions with the protein (Chang et al, 2010 …”