Chemical Stabilization of Conformational States of Aspartate Transcarbamoylase

Cross-linking of the protein with bifunctional reagents offers the prospects of stabilizing various functional states and thus clarifying the structure–function relationship. This approach has been applied to the other enzymes of a similar nature. In selecting the most appropriate bifunctional reagent, some important considerations are the desirable length of the cross-linkage, whether it can be cleaved subsequently under controlled conditions, the type of amino acid side chains that will be modified, and methods for estimating the extent of cross-linking. It would be interesting to use a bifunctional reagent similar to tartryl diazide but containing a disulfide linkage that could be cleaved without affecting enzyme activity. Various hybrids can be prepared by the reassociation of the cross-linked and unmodified subunits or subunits from derivatives cross-linked under different conditions. Control experiments can be performed by allowing the two types of subunits isolated from one cross-linked derivative to reassociate.