Plant tumour biocontrol agent employs a tRNA-dependent mechanism to inhibit leucyl-tRNA synthetase.
Leucyl-tRNA synthetases (LeuRSs) have an essential role in translation and are promising targets for antibiotic development. Agrocin 84 is a LeuRS inhibitor produced by the biocontrol agent Agrobacterium radiobacter K84 that targets pathogenic strains of A. tumefaciens, the causative agent of plant tumours. Agrocin 84 acts as a molecular Trojan horse and is processed inside the pathogen into a toxic moiety (TM84). Here we show using crystal structure, thermodynamic and kinetic analyses, that this natural antibiotic employs a unique and previously undescribed mechanism to inhibit LeuRS. TM84 requires tRNA(Leu) for tight binding to the LeuRS synthetic active site, unlike any previously reported inhibitors. TM84 traps the enzyme-tRNA complex in a novel 'aminoacylation-like' conformation, forming novel interactions with the KMSKS loop and the tRNA 3'-end. Our findings reveal an intriguing tRNA-dependent inhibition mechanism that may confer a distinct evolutionary advantage in vivo and inform future rational antibiotic design.
Department of Cell Biology and Physiology, The University of North Carolina at Chapel Hill, 536 Taylor Hall, CB# 7090, Chapel Hill, North Carolina 27599-7090, USA.
Shaileja
S
Chopra
Andrés
A
Palencia
Cornelia
C
Virus
Ashutosh
A
Tripathy
Brenda R
BR
Temple
Adrian
A
Velazquez-Campoy
Stephen
S
Cusack
John S
JS
Reader
D000227:Adenine Nucleotides / Q000737:chemistry / Q000494:pharmacology*; D016960:Agrobacterium tumefaciens / Q000187:drug effects / Q000201:enzymology*; D049148:Aminoacylation / Q000187:drug effects; D061046:Biological Control Agents; D002151:Calorimetry; D018360:Crystallography, X-Ray; D004791:Enzyme Inhibitors / Q000737:chemistry / Q000494:pharmacology; D007935:Leucine-tRNA Ligase / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000378:metabolism; D008958:Models, Molecular; D010941:Plant Tumors / Q000382:microbiology*; D011485:Protein Binding / Q000187:drug effects; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D018749:RNA, Plant / Q000737:chemistry / Q000378:metabolism*; D012343:RNA, Transfer / Q000737:chemistry / Q000378:metabolism*
D000227:Adenine Nucleotides; D061046:Biological Control Agents; D004791:Enzyme Inhibitors; D018749:RNA, Plant; C013799:agrocin 84; D012343:RNA, Transfer; D007935:Leucine-tRNA Ligase