Structural Insight into Caenorhabditis elegans Sex-determining Protein FEM-2

• Published in: The Journal of biological chemistry 2013-07, Vol.288 (30), p.22058-22066
• Main Authors: Zhang, Yi, Zhao, Haifeng, Wang, Jia, Ge, Jingpeng, Li, Yang, Gu, Jinke, Li, Peng, Feng, Yue, Yang, Maojun
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Animals; Binding Sites - genetics; Blotting, Western; C. elegans; Caenorhabditis elegans - genetics; Caenorhabditis elegans - growth & development; Caenorhabditis elegans - metabolism; Caenorhabditis elegans Proteins - chemistry; Caenorhabditis elegans Proteins - genetics; Caenorhabditis elegans Proteins - metabolism; Cell Cycle Proteins - genetics; Cell Cycle Proteins - metabolism; Crystallography, X-Ray; FEM-2; HEK293 Cells; Humans; Male; Models, Molecular; Molecular Sequence Data; Mutation; Novel Fold; Phosphoprotein Phosphatases - chemistry; Phosphoprotein Phosphatases - genetics; Phosphoprotein Phosphatases - metabolism; Phosphorylation; Protein Binding; Protein Phosphatase; Protein Structure; Protein Structure and Folding; Protein Structure, Tertiary; Sequence Homology, Amino Acid; Sex Determination; Sex Determination Processes - genetics; Structural Biology; Substrate; X-ray Crystallography
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M113.464339

In the nematode Caenorhabditis elegans, fem-1, fem-2, and fem-3 play crucial roles in male sexual development. Among these three genes, fem-2 encodes a PP2C (serine/threonine phosphatase type 2C)-like protein, whose activity promotes the development of masculinity. Different from the canonical PP2Cs, FEM-2 consists of an additional N-terminal domain (NTD) apart from its C-terminal catalytic domain. Interestingly, genetic studies have indicated indispensable roles for both of these two domains of FEM-2 in promoting male development, but the underlying mechanism remains unknown. In the present study, we solved the crystal structure of full-length FEM-2, which revealed a novel structural fold formed by its NTD. Structural and functional analyses demonstrated that the NTD did not directly regulate the in vitro dephosphorylation activity of FEM-2, but instead functioned as a scaffold domain in the assembly of the FEM-1/2/3 complex, the executioner in the final step of the sex determination pathway. Biochemical studies further identified the regions in the NTD involved in FEM-1 and FEM-3 interactions. Our results not only identified a novel fold formed by the extra domain of a noncanonical PP2C enzyme, but also provided important insights into the molecular mechanism of how the NTD works in mediating the sex-determining role of FEM-1/2/3 complex. Background: FEM-2 is central to the sex determination pathway in C. elegans. Results: The N-terminal domain (NTD) of FEM-2 binds to FEM-1 and FEM-3, but does not directly regulate the phosphatase activity of FEM-2. Conclusion: The FEM-2 NTD functions as a scaffold in sex determination. Significance: This work reveals how the novel folded NTD facilitates the role of FEM-2 in sex determination.