Disulfide crosslinks to probe the structure and flexibility of a designed four‐helix bundle protein

The introduction of disulfide crosslinks is a generally useful method by which to identify regions of a protein that are close together in space. Here we describe the use of disulfide crosslinks to investigate the structure and flexibility of a family of designed 4-helix bundle proteins. The results of these analyses lend support to our working model of the proteins' structure and suggest that the proteins have limited main-chain flexibility.