Fig. 1: Crystal structures of the cytosolic domain of human Fis1 in different conformations.

A New crystal structure of Fis1_ΔTM (Form 1) containing two Fis1_ΔTM molecules (green and light green) in the asymmetric unit with a structure identical to that of the previously reported Fis1_ΔTM structure (PDB code: 1NZN) except for the space group of crystal. B The new crystal structure of Fis1_ΔTM Form 2 reveals the presence of an N-terminal Fis1 arm. C Comparison of different structures of Fis1, human Form 2 (this study, orange), the previously reported crystal structure (cyan, PDB code: 1NZN), the previously reported NMR structure (partially covers the TM region, magenta, PDB code: 1PC2), and the previously reported yeast Fis1_ΔTM (gray, PDB code: 3O48). The α1 (cyan) of the previous structure, α1 A and α1B helices (orange) of the Form 2 structure were indicated. D The hydrogen bond networks that stabilize the N-terminal Fis1 arm (α1A) with α2 and α4 on the concave surface. The side chain and the main chains of the residues involved in the interaction are shown as sticks and lines, respectively. Hydrophobic interaction of Met1 and Leu3 in α1A with residues from the α4 and α6 helices. E The electrostatic surface potentials of the concave regions in the different crystal structures of Fis1_∆TM and human Fis1_∆TM Form 1 in this study. The long α1 helix of the neighboring Fis1_∆TM molecule in the dimer is shown in cyan (left). For human Fis1_∆TM Form 2 in this study (middle) and the yeast Fis1_∆TM (right, PDB code: 3O48) structures, N-terminal Fis1 arms from their own subunits are shown in orange.