The Structural Studies Of SPRY7 And RNF135 Proteins

The SPRY/B30.2 domain is one of the most abundant protein folds in eukaryote genomes,and SPRY domains are found in hundreds of human proteins.Most SPRY domains are expected to mediate protein-protein interactions,but their target proteins as well as the structural basis for the interactions are largely unknown.The SPRY7 protein is encoded by the spryd7 gene,also known as the chronic lymphocytic leukemia deletion region gene 6(CLLD6)protein or C13of1.SPRY7 contains one SPRY domain,and unlike most other SPRY domain-containing proteins,SPRY7 contains no additional domains.Three-dimensional structure and biological functions of SPRY7 are still unclear.In this study,human SPRY7 proteins with different N-and C-terminal truncations were recombinantly expressed and purified.The domain boundaries and structural features of the SPRY domain of SPRY7 protein were analyzed using solution nuclear magnetic resonance(NMR).The appropriate constructs were selected for protein crystallization and X-ray diffraction.For the first time,the crystal structure of the SPRY domain of SPRY7 protein in the apo state was then determined at a resolution of 1.62 (?),and compared to other previously reported SPRY domain structures,some unique aspects of the SPRY7 protein in structure and surface charge were found.The research results provide an important basis for understanding of the structure and function of SPRY7.RNF135(also known as Riplet,RUEL)is an E3 ubiquitin ligase containing a SPRY domain.RNF135 has multiple biological functions,including mediating the poly-ubiquitination of the intracellular RNA virus receptor RIG-I to promote innate immunity response,but the threedimensional structure of the RNF135 protein SPRY domain has not yet been resolved.In this study,RNF135 SPRY domain fragments were analyed by solution NMR,and it was found that deletion of the N-terminal region of the SPRY domain has very little impact on its overall structure.These results will help further structural studies on the protein.