The domain of unknown function (DUF) YP001302112.1, a protein secreted by the human intestinal microbita, has been determined by NMR and represents the first structure for the Pfam PF14466. Its NMR structure is classified as a new fold, which, nonetheless, shows limited similarities with representatives of the PLAT/LH2 domains from PF01477 and the C2 domains from PF00168, both of which bind Ca21 for their physiological functions. Further experiments revealed affinity of YP001302112.1 for Ca21, and the NMR structure in the presence of CaCl2 was better defined than that of the apo-protein. Overall, these NMR structures establish a new connection between structural representatives from two widely different Pfams that include the calcium-binding domain of a sialidase from Vibrio cholerae and the a-toxin from Clostridium perfrigens, whereby these two proteins have only 7% sequence identity. Furthermore, it provides information toward the functional annotation of YP001302112.1, based on its capacity to bind Ca21, and thus adds to the structural and functional coverage of the protein sequence universe.
- Calcium-binding protein
- Functional annotation of a DUF
- Human gut microbiome
- Structural coverage of the protein sequence universe