Molecular Modeling and Structure Analysis of S100 Calcium Binding Protein A14

S100 calcium binding protein A14 (S100A14), a new member of S100 calcium binding protein, has been rarely studied and its structure and function are still unclear. In this study, a credible model of human S100A14 (residues 12-102) was built based on the molecular structure of human S100A13 (Swiss-rot Q99584, PDB ID:1YUR_A). Protein sequence alignment showed some mutations in Ca2+-binding domain in the C-terminal, which suggested the C-terminal might not be able to bind Ca2+. While most of the Cu2+/Zn2+ binding sites of S100 protein family were conserved in S100A14, strongly suggesting its binding affinity to Cu2+ and Zn2+. Compare to S100A13, the secondary structure showed there was a longer extension in the helix I and helix IV of S100A14. An unique site Trp (S100A13: W77), reported to play an important role in the interaction between S100A13 and cytoplasmic membrane, was also exist in S100A14 (W85), which suggested S100A13 and S100A14 might have common biological function. Though the monomer structures of S100A13 and S100A14 were quite similar, the strong difference between their C-terminals indicated S100A14 might have its functional uniqueness since the functional specificity of S100 proteins mainly attributes to the C-terminal sequence variation.