Figure 2.
Flexible arm feature of eNOS compared to bacterial NOS (bsNOS) and cytochrome P450. Panel A demonstrates the structural similarity of bsNOS (magenta) and eNOS (yellow). The N-terminal end of bsNOS begins immediately after the flexible arm region (red) of eNOS. Thus, bsNOS is deficient in both the redox regulation. Panel B demonstrates the superposition of open (yellow) and closed (magenta) conformations of P450. This flexible region of P450 controls substrate access to the heme and thus serves the same function as the eNOS flexible arm. However, as the P450 lacks the ZnS4 cluster, it is not susceptible to redox regulation.