protein kinase C conserved region 1 (C1 domain) found in the myotubularin-related protein Sbf and similar proteins
This group includes Drosophila melanogaster SET domain binding factor (Sbf), the single homolog of human MTMR5/MTMR13, and similar proteins, that show high sequence similarity to vertebrate myotubularin-related proteins (MTMRs) which may function as guanine nucleotide exchange factors (GEFs). Sbf is a pseudophosphatase that coordinates both phosphatidylinositol 3-phosphate (PI(3)P) turnover and Rab21 GTPase activation in an endosomal pathway that controls macrophage remodeling. It also functions as a GEF that promotes Rab21 GTPase activation associated with PI(3)P endosomes. Vertebrate MTMR5 and MTMR13 contain an N-terminal DENN domain, a PH-GRAM domain, an inactive PTP domain, a SET interaction domain, a coiled-coil domain, and a C-terminal PH domain. Members of this family contain these domains and have an additional C1 domain. This model corresponds to the C1 domain. The C1 domain is a cysteine-rich zinc binding domain that does not bind DNA nor possess structural similarity to conventional zinc finger domains; it contains two separate Zn(2+)-binding sites.