Download MendeleyThe X-Ray Structure of (Mebm2T)1-Cyclosporin Complexed with Cyclophilin a Provides an Explanation for its Anomalously High Immunosuppressive Activity.
Mikol, V., Kallen, J., Walkinshaw, M.D.(1994) Protein Eng 7: 597
- PubMed: 8073029
- DOI: https://doi.org/10.1093/protein/7.5.597
- Primary Citation of Related Structures:
1CWB - PubMed Abstract:
For most of the cyclosporin A (CsA) analogs, there is generally a good correlation between cyclophilin binding and immunosuppression. However, this relationship does not seem to hold for 4-[(E)-2-butenyl]-4,4,N-trimethyl-L-threonine1 (MeBm2t)1-CsA. Its affinity for cyclophilin was reported to be approximately 1% that of CsA and its immunosuppressive activity in vitro was shown to be approximately 30% that of CsA. We report here the crystal structure of a complex between recombinant human cyclophilin A (CypA) and (MeBm2t)1-CsA which has been determined by X-ray crystallography at 2.2 A resolution and refined to an R-factor of 16.3%. (MeBm2t)1-CsA shows a similar bound conformation and network of interactions to CypA as CsA. The measured lower affinity for CypA cannot therefore be explained by a different mode of binding. We propose that the poor affinity to CypA could be accounted for by the existence of an equilibrium in aqueous solution between a 'cyclophilin bound conformation' and a 'non-binding conformation' of (MeBm2t)1-CsA. The relatively high immunosuppressive activity is suggested to result from slight conformational differences observed in the effector domain.
Organizational Affiliation:
Sandoz AG, Basle, Switzerland.
