Domain Swap experiment

DNA binding could result in a general conformational change that allows the bound protein to activate transcription, or these two functions could be served by separate and independent domains. Domain swap experiments suggest that the latter is the case. 

When one inspects the multiple channel protein sequences that have been derived, one readily recognizes that they have related primary sequences. This suggests that they have similar three-dimensional structures. The primary sequences can be subdivided into an amino-terminal, a core and a carboxy-terminal domain (see Fig. 5). Each domain seems to contribute separately to the structure and function of a given channel [49]. Following this hypothesis, it has been possible to carry out domain swapping experiments between Sh and RCK proteins [49] as well as between... 

The first data concerning the structmal requirements for communication with the transcription apparatus came from domain swapping experiments with the GAL4 protein of yeast. 

Direct repressors interact with the basal components of the transcription apparatus or with transcriptional activators to inhibit their activity. Specific repressors, analogous to transcriptional activators, are constructed modularly, with a DNA-binding domain and a repressor domain. The repressive character of such domains has been proven in domain swapping experiments. The mechanism of specific repression remains speculative. The following mechanisms are, however, conceivable ... 

The results of domain swap experiments, in which an extracellular domain of one kind of cadherin is replaced with the corresponding domain of a different cadherin, have indicated that the specificity of binding resides, at least in part, in the most distal extracellular domtiin, the N-terminal domain. In the past, cadherin-mediated adhesion was commonly thought to require only head-to-head Interactions between the N-terminal domains of cadherin oligomers on adjacent cells, as depicted in Figure 6-3. However, the results of some experiments suggest that under some experimental conditions at least three cadherin domains from each molecule, not just the N-terminal domains, participate by inter-digitation in trans associations. 

Further evidence that the subdomains are functionally equivalent came from domain swapping experiments (Figure 10) that produced two unusual constructs. One molecule consisted of the CAD GLN domain fused to two tandem copies of CPS.A and a second in which the location of the CPS subdomain were switched to give a molecule in the arrangement GLN-CPS.B-CPS.A. Both of these constructs were fully functional CPSases. Interestingly, only the latter species retains sensitivity to allosteric effectors. 

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