title: A synthetic peptidoglycan fragment as a competitive inhibitor of the melanization cascade.
abstract: Melanin synthesis is essential for defense and development but must be tightly controlled because systemic hyperactivation of the prophenoloxidase and excessive melanin synthesis are deleterious to the hosts. The melanization cascade of the arthropods can be activated by bacterial lysine-peptidoglycan (PGN), diaminopimelic acid (DAP)-PGN, or fungal beta-1,3-glucan. The molecular mechanism of how DAP- or Lys-PGN induces melanin synthesis and which molecules are involved in distinguishing these PGNs are not known. The identification of PGN derivatives that can work as inhibitors of the melanization cascade and the characterization of PGN recognition molecules will provide important information to clarify how the melanization is regulated and controlled. Here, we report that a novel synthetic Lys-PGN fragment ((GlcNAc-MurNAc-L-Ala-D-isoGln-L-Lys-D-Ala)2, T-4P2) functions as a competitive inhibitor of the natural PGN-induced melanization reaction. By using a T-4P2-coupled column, we purified the Tenebrio molitor PGN recognition protein (Tm-PGRP) without causing activation of the prophenoloxidase. The purified Tm-PGRP recognized both Lys- and DAP-PGN. In vitro reconstitution experiments showed that Tm-PGRP functions as a common recognition molecule of Lys- and DAP-PGN-dependent melanization cascades.
authors.affiliation: National Research Laboratory of Defense Proteins, College of Pharmacy, Pusan National University, Kumjeong Ku, Busan 609-735, Korea.
authors.forename: Ji Won
authors.initials: JW
authors.lastname: Park
authors.forename: Byung-Rok
authors.initials: BR
authors.lastname: Je
authors.forename: Shunfu
authors.initials: S
authors.lastname: Piao
authors.forename: Seiichi
authors.initials: S
authors.lastname: Inamura
authors.forename: Yukari
authors.initials: Y
authors.lastname: Fujimoto
authors.forename: Koichi
authors.initials: K
authors.lastname: Fukase
authors.forename: Shoichi
authors.initials: S
authors.lastname: Kusumoto
authors.forename: Kenneth
authors.initials: K
authors.lastname: Söderhäll
authors.forename: Nam-Chul
authors.initials: NC
authors.lastname: Ha
authors.forename: Bok Luel
authors.initials: BL
authors.lastname: Lee
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002240:Carbohydrate Sequence; D004156:Catechol Oxidase / Q000737:chemistry; D018076:DNA, Complementary / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004331:Drosophila melanogaster / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D004792:Enzyme Precursors / Q000737:chemistry; D006026:Glycoside Hydrolases / Q000737:chemistry; D006458:Hemolymph / Q000378:metabolism; D019476:Insect Proteins / Q000737:chemistry; D008239:Lysine / Q000737:chemistry; D008543:Melanins / Q000737:chemistry*; D008956:Models, Chemical; D008969:Molecular Sequence Data; D010457:Peptidoglycan / Q000737:chemistry*; D011108:Polymers / Q000737:chemistry; D011485:Protein Binding; D011994:Recombinant Proteins / Q000737:chemistry; D013712:Tenebrio / Q000378:metabolism; D047071:beta-Glucans / Q000737:chemistry
chemical_list: D018076:DNA, Complementary; D004792:Enzyme Precursors; D019476:Insect Proteins; D008543:Melanins; D010457:Peptidoglycan; D011108:Polymers; D011994:Recombinant Proteins; D047071:beta-Glucans; C033363:beta-1,3-glucan; C038451:pro-phenoloxidase; D004156:Catechol Oxidase; D006026:Glycoside Hydrolases; C026255:endo-N-acetylmuramidase; D008239:Lysine