Structure of tracheal cytotoxin in complex with a heterodimeric pattern-recognition receptor.
Tracheal cytotoxin (TCT), a naturally occurring fragment of Gram-negative peptidoglycan, is a potent elicitor of innate immune responses in Drosophila. It induces the heterodimerization of its recognition receptors, the peptidoglycan recognition proteins (PGRPs) LCa and LCx, which activates the immune deficiency pathway. The crystal structure at 2.1 angstrom resolution of TCT in complex with the ectodomains of PGRP-LCa and PGRP-LCx shows that TCT is bound to and presented by the LCx ectodomain for recognition by the LCa ectodomain; the latter lacks a canonical peptidoglycan-docking groove conserved in other PGRPs. The interface, revealed in atomic detail, between TCT and the receptor complex highlights the importance of the anhydro-containing disaccharide in bridging the two ectodomains together and the critical role of diaminopimelic acid as the specificity determinant for PGRP interaction.
Chang
Chung-I
CI
Howard Hughes Medical Institute, University of Texas Southwestern Medical Center at Dallas, 6001 Forest Park Road, Dallas, TX 75390-9050, USA.
Chelliah
Yogarany
Y
Borek
Dominika
D
Mengin-Lecreulx
Dominique
D
Deisenhofer
Johann
J
D000595:Amino Acid Sequence; D000818:Animals; D002352:Carrier Proteins / Q000737:chemistry* / Q000378:metabolism; D003460:Crystallization; D018360:Crystallography, X-Ray; D003603:Cytotoxins / Q000737:chemistry* / Q000378:metabolism; D004331:Drosophila melanogaster; D006860:Hydrogen Bonding; D057927:Hydrophobic and Hydrophilic Interactions; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010457:Peptidoglycan / Q000737:chemistry* / Q000378:metabolism; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary
D002352:Carrier Proteins; D003603:Cytotoxins; D010457:Peptidoglycan; C118897:peptidoglycan recognition protein