Figure 5
Structural comparison of cis- and trans isomers with T-state insulin structures. (a) The cis- and (b) trans isomers represent T-state insulins with conserved B-chain structures (cyan). The cis isomer has a poorly defined A1-A8 helix (dotted line), whereas the two trans isomers in the crystallographic asymmetric unit both display a Class 1 A1-A8 helix. (c) The two insulin structures within the asymmetric unit of PDB entry 1MSO aligned across their B chain helices, showing both a Class 1 (light blue) and Class 2 (dark blue) A1-A8 helix. (d) (2mF obs − DF calc) difference electron density associated with the residues within the N- and C-terminal helices of the A chain of the cis isomer; contour level: 1 σ. (e) (2mF obs − DF calc) difference electron density in the vicinity of the A6-A11 dicarba bond (arrowed) within the trans isomer, contour level: 1.3 σ. (f) A zoom-in view of the boxed selection in panel (c) highlighting the differences in the A2, A3 and A4 side-chain positions of the two different classes. Analysis of molecular dynamics data of (g) cis isomer (h) trans isomer and (i) insulin, showing RMSDs of all atoms of residues GlyA1 to GluA4 for each simulation frame with respect to a representative Class 2 conformation structure (referred to as T-wide here). Regions corresponding to the Class 2 conformation are shaded yellow. Average RMSDs over all simulation frames for insulin, cis isomer and trans isomer are 3.0 ± 0.9 Å, 3.4 ± 1.3 Å and 3.5 ± 1.0 Å, respectively. Note that each bin between pairs of tick marks on the horizontal axis represents a separate 200 ns simulation.
