1s7p
From Proteopedia
Solution structure of thermolysin digested microcin J25
Structural highlights
FunctionMCJA_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 structure of a two-chain peptide formed by the treatment of the potent antimicrobial peptide microcin J25 (MccJ25) with thermolysin has been characterized by NMR spectroscopy and mass spectrometry. The native peptide is 21 amino acids in size and has the remarkable structural feature of a ring formed by linkage of the side chain of Glu8 to the N-terminus that is threaded by the C-terminal tail of the peptide. Thermolysin cleaves the peptide at the Phe10-Val11 amide bond, but the threading of the C-terminus through the N-terminal ring is so tight that the resultant two chains remain associated both in the solution and in the gas phases. The three-dimensional structure of the thermolysin-cleaved peptide derived using NMR spectroscopy and simulated annealing calculations has a well-defined core that comprises the N-terminal ring and the threading C-terminal tail. In contrast to the well-defined core, the newly formed termini at residues Phe10 and Val11 are disordered in solution. The C-terminal tail is associated to the ring both by hydrogen bonds stabilizing a short beta-sheet and by hydrophobic interactions. Moreover, unthreading of the tail through the ring is prevented by the bulky side chains of Phe19 and Tyr20, which flank the octapeptide ring. This noncovalent two-peptide complex that has a remarkable stability in solution and in highly denaturing conditions and that survives in the gas phase is the first example of such a two-chain peptide lacking disulfide or interchain covalent bonds. Structure of thermolysin cleaved microcin J25: extreme stability of a two-chain antimicrobial peptide devoid of covalent links.,Rosengren KJ, Blond A, Afonso C, Tabet JC, Rebuffat S, Craik DJ Biochemistry. 2004 Apr 27;43(16):4696-702. PMID:15096038[4] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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