| Popis: |
The complement protein (CP) molecule (also known as SCR, CCP or sushi domain) is prevalent amongst proteins that regulate complement activation. Functional and mutagenesis studies have shown that in most cases two or more neighbouring CP modules comprise specific interaction sites for other molecules. Hence the orientation in space of a CP module with respect to its neighbours and the flexibility of the intermodular junction are likely to be critical for function. The Vaccinia virus complement control protein (VCP) is a complement regulator composed in its entirety of four tandemly arranged CP modules. The central two modules of this protein have been successfully expressed in Pichia pastoris and the structure of the modules, numbers 2 and 3 (VCP~2, 3), solved using NMR spectroscopy. Each module has a typical CP module structure and the two modules do not share an extensive interface. Inspection of fifty structures calculated independently on the basis of the NMR-derived data revealed that the inter-modular orientation does not vary much implying that the 40 linker-to-module NOEs limit the possible movement of the two modules relative to one another during the structure calculation. Module 2 contains a five residue insertion and has a more elongated appearance than module 3. Module 3 appears bulkier due to the laterally protruding hypervariable loop. Module 3 from VCP~2,3 differs a little in structure from module 3 from the VCP~3, 4 module pair. The structure of VCP~2, allowed reconstruction of VCP~2,3,4 and provides a means of gaining structural information about VCP as a whole using a dissect and rebuild strategy. A recent crystal structure of intact VCP exhibits a somewhat different orientation of the two central modules. |
