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Structural and biophysical analysis of nuclease protein antibiotics

DOI: 10.1042/BCJ20160544 DOI Help

Authors: Alexander Klein (University of Oxford) , Justyna Wojdyla (University of Oxford) , Amar Joshi (University of Oxford) , Inokentijs Josts (University of Glasgow) , L. C. Mccaughey (University of Glasgow) , N. Housden (University of Oxford) , R. Kaminska (University of Oxford) , Olwyn Byron (University of Glasgow) , D. Walker (University of Glasgow) , C. Kleanthous (University of Oxford)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Biochemical Journal

State: Published (Approved)
Published: July 2016
Diamond Proposal Number(s): 12346

Open Access Open Access

Abstract: Protein antibiotics (bacteriocins) are a large and diverse family of multidomain toxins that kill specific Gram-negative bacteria during intraspecies competition for resources. Our understanding of the mechanism of import of such potent toxins has increased significantly in recent years especially with the reporting of several structures of bacteriocin domains. Less well understood is the structural biochemistry of intact bacteriocins and how these compare across bacterial species. Here we focus on endonuclease (DNase) bacteriocins that target the genomes of Escherichia coli and Pseudomonas aeruginosa , known as E-type colicins and S-type pyocins, respectively, bound to their specific immunity (Im) proteins. First, we report the 3.2 Å structure of the DNase colicin ColE9 in complex with its ultra-high affinity immunity protein, Im9. In contrast to Im3, which when bound to the ribonuclease (rRNase) domain of the homologous colicin ColE3 makes contact with the translocation (T-) domain of the toxin, we find that Im9 makes no such contact and only interactions with the ColE9 cytotoxic domain are observed. Second, we report small angle X-ray scattering (SAXS) data for two S-type DNase pyocins, S2 and AP41, into which are fitted recently determined X-ray structures for isolated domains. We find that DNase pyocins and colicins are both highly elongated molecules even though the order of their constituent domains differs. We discuss the implications of these architectural similarities and differences in the context of the translocation mechanism of protein antibiotics through the cell envelope of Gram-negative bacteria.

Subject Areas: Biology and Bio-materials, Medicine, Physics


Instruments: B21-High Throughput SAXS , I02-Macromolecular Crystallography