CRYSTAL STRUCTURE OF A TRAP PERIPLASMIC SOLUTE BINDING PROTEIN FROM VERMINEPHROBACTER EISENIAE EF01-2 (Veis_3954, TARGET EFI-510324) A NEPHRIDIAL SYMBIONT OF THE EARTHWORM EISENIA FOETIDA, BOUND TO D-ERYTHRONATE WITH RESIDUAL DENSITY SUGGESTIVE OF SUPERPOSITION WITH COPURIFIED ALTERNATIVE LIGAND.