title: Walkmycin B targets WalK (YycG), a histidine kinase essential for bacterial cell growth.
abstract: The WalK (a histidine kinase)/WalR (a response regulator, aka YycG/YycF) two-component system is indispensable in the signal transduction pathway for the cell-wall metabolism of Bacillus subtilis and Staphylococcus aureus. The inhibitors directed against WalK would be expected to have a bactericidal effect. After we screened 1368 culture broths of Streptomyces sp. by a differential growth assay, walkmycin A, B and C, which were produced by strain MK632-100F11, were purified using silica-gel column chromatography and HPLC. In this paper, the chemical structure of the major product (walkmycin B) was determined to be di-anthracenone (C(44)H(44)Cl(2)O(14)), which was very similar to BE40665A. MICs of walkmycin B against B. subtilis and S. aureus were 0.39 and 0.20 microg ml(-1), and IC(50) measurements against WalK were 1.6 and 5.7 microM, respectively. To clarify the affinity between WalK and walkmycin B, surface plasmon resonance was measured to obtain the equilibrium dissociation constant, K(D1), of 7.63 microM at the higher affinity site of B. subtilis WalK. These results suggest that walkmycin B inhibits WalK autophosphorylation by binding to the WalK cytoplasmic domain.
authors.affiliation: Department of Bioscience, Graduate School of Agriculture, Kinki University, Nara, Japan.
authors.forename: Ario
authors.initials: A
authors.lastname: Okada
authors.forename: Masayuki
authors.initials: M
authors.lastname: Igarashi
authors.forename: Toshihide
authors.initials: T
authors.lastname: Okajima
authors.forename: Naoko
authors.initials: N
authors.lastname: Kinoshita
authors.forename: Maya
authors.initials: M
authors.lastname: Umekita
authors.forename: Ryuichi
authors.initials: R
authors.lastname: Sawa
authors.forename: Kunio
authors.initials: K
authors.lastname: Inoue
authors.forename: Takafumi
authors.initials: T
authors.lastname: Watanabe
authors.forename: Akihiro
authors.initials: A
authors.lastname: Doi
authors.forename: Aaron
authors.initials: A
authors.lastname: Martin
authors.forename: John
authors.initials: J
authors.lastname: Quinn
authors.forename: Yoshio
authors.initials: Y
authors.lastname: Nishimura
authors.forename: Ryutaro
authors.initials: R
authors.lastname: Utsumi
mesh_terms: D000873:Anthracenes / Q000737:chemistry / Q000494:pharmacology*; D000900:Anti-Bacterial Agents / Q000737:chemistry / Q000494:pharmacology*; D001419:Bacteria / Q000187:drug effects; D015394:Molecular Structure; D011494:Protein Kinases / Q000378:metabolism*; D013302:Streptomyces / Q000201:enzymology
chemical_list: D000873:Anthracenes; D000900:Anti-Bacterial Agents; C548104:walkmycin B; D011494:Protein Kinases; C515949:YycG protein, Staphylococcus epidermidis