6AYH Salmonella enterica GusR Salmonella choleraesuis 6AYI Escherichia coli GusR Escherichia coli O157:H7 7QEE SN243 mutant D415N bound to para-nitrophenyl-Beta-D-glucuronide Synthetic construct 7QEF Crystal structure of para-nitrophenyl-Beta-D-glucuronide bound to a mutant of SN243 (D415A) Synthetic construct