Loop Structures in AKRs


Using the secondary structure of rat liver 3α-HSD (AKR1C9) as a template the positions of β-sheets, α-helices and the three large loops can be assigned.

  • B1 (7-9), B2 (15-17), H1(239-248) and H2 (290-298) are β-sheets and α-helices, respectively not in the core of the (α/β) 8-barrel structure.
  • Positions of α-helices are: α1 (32-43), α2 (58-70), α3 (95-106), α4 (144-156), α5 (170-177), α6 (200-209), α7 (252-262) and α8 (274-280).
  • Positions of β-strands in the barrel are: β1 (20-22), β2 (48-50), β3 (80-85), β4 (111-116), β5 (160-166), β6 (188-192), β7 (212-216), and β8 (265-269).
  • Loop A is located from 117-143, loop B is located at 217-238 and loop C is located from 299-322.
  • Residues involved in cofactor binding are: T(24), D(50), S(166), N(167), Q(190), Y(216), S(221), R(270), S(271), R(276), E(279), and N(280).
  • Residues involved in substrate binding are: T(24), L(54), F(118), F(129), T(226), W(227), N(306) and Y(310).
  • Residues involved in catalysis are: D(50), Y(55), K(84) and H(117).
  • All residues are numbered relative to 3α-HSD structure.