1pp5
From Proteopedia
Structure of Antibacterial Peptide Microcin J25: a 21-Residue Lariat Protoknot
Structural highlights
Function[MCJA_ECOLX] Peptide antibiotic that functions through inhibition of the bacterial DNA-dependent RNA polymerase (RNAP). May inhibit transcription by binding in RNAP secondary channel and blocking nucleotide substrates access to the catalytic center. Exhibits potent bacteriocidal activity against a range of Enterobacteriaceae, including several pathogenic E.coli, Salmonella and Shigella strains. Also acts on the cytoplasmic membrane of Salmonella newport, producing alteration of membrane permeability and disruption of the subsequent gradient dissipation, which inhibits several processes essential for cell viability, such as oxygen consumption. Induces bacterial filamentation in susceptible cells in a non-SOS-dependent way, but this phenotype may result from impaired transcription of genes coding for cell division proteins.[1] [2] [3] Publication Abstract from PubMedThe 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. Structure of antibacterial peptide microcin J25: a 21-residue lariat protoknot.,Bayro MJ, Mukhopadhyay J, Swapna GV, Huang JY, Ma LC, Sineva E, Dawson PE, Montelione GT, Ebright RH J Am Chem Soc. 2003 Oct 15;125(41):12382-3. PMID:14531661[4] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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