A synthetic peptidoglycan fragment as a competitive inhibitor of the melanization cascade.
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.
Park
Ji Won
JW
National Research Laboratory of Defense Proteins, College of Pharmacy, Pusan National University, Kumjeong Ku, Busan 609-735, Korea.
Je
Byung-Rok
BR
Piao
Shunfu
S
Inamura
Seiichi
S
Fujimoto
Yukari
Y
Fukase
Koichi
K
Kusumoto
Shoichi
S
Söderhäll
Kenneth
K
Ha
Nam-Chul
NC
Lee
Bok Luel
BL
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
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