Steve Ealick's Research Group


Burkholderia glumae ToxA


PDB files:

5JE6 ToxA

5JDZ ToxA/SAH

5JE0 ToxA/SAH/1,6-DDMT

5JE1 ToxA/SAH/toxoflavin

5JE2 ToxA-Y7F/SAH

5JDY ToxA-Y7F/SAH/toxoflavin

5JE3 ToxA-Y7A/SAH

5JE4 ToxA-Y7A/SAH/toxoflavin

5JE5 ToxA/SAH/1-DMT

Description:

Toxoflavin is a major virulence factor of the rice pathogen Burkholderia glumae.  The tox operon of B. glumae contains five putative toxoflavin biosynthetic genes toxABCDE.  ToxA is a predicted S-adenosylmethionine dependent methyltransferase and toxA knockouts of B. glumae are less virulent in plant infection models.  Here we show that ToxA performs two consecutive methylations to convert the putative azapteridine intermediate, 1,6-didemethyltoxoflavin, to toxoflavin.  Our crystal structures of complexes reveal the molecular basis of the dual methyltransferase activity.

The structure of ToxA contains a Class I methyltransferase fold having an N-terminal extension that either closes over the active site or is largely disordered.


Click the image to enlarge.


Apo ToxA forms a homodimer having noncrystallographic twofold symmetry (top). In contrast, ligands interfere with homodimer formation, so the structures of complexes tend to be monomeric.


Click the image to enlarge.


Toxoflavin binds in a deep slot between the Class I methyltransferase domain and the flap domain.


Click the image to enlarge.


Reference

Fenwick MK, Philmus B, Begley TP, and Ealick SE. Burkholderia glumae ToxA is a Dual Specificity Methyltransferase that Catalyzes the Last Two Steps of Toxoflavin Biosynthesis. Biochemistry 55:2748-2759 (2016).



Contacts Procedures Structures Projects Publications Lab Home Page Group Members