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Structure of antibacterial peptide microcin J25: a 21-residue lariat protoknot
Marvin J Bayro1, Jayanta Mukhopadhyay, G V T Swapna
1Department of Molecular Biology and Biochemistry, Waksman Institute, and Howard Hughes Medical Institute, Rutgers University, Piscataway, New Jersey 08854, USA.
Abstract:
The antibacterial peptide microcin J25 (MccJ25) inhibits bacterial transcription by binding within, and obstructing, the nucleotide-uptake channel of bacterial RNA polymerase. Published covalent and three-dimensional structures indicate that MccJ25 is a 21-residue cycle. Here, we show that the published covalent and three-dimensional structures are incorrect, and that MccJ25 in fact is a 21-residue "lariat protoknot", consisting of an 8-residue cyclic segment followed by a 13-residue linear segment that loops back and threads through the cyclic segment. MccJ25 is the first example of a lariat protoknot involving a backbone-side chain amide linkage.
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