The function of OBSCN (obscurin, cytoskeletal calmodulin and titin-interacting RhoGEF, Ensembl gene identifier ENSG00000154358) is as follows. Structural component of striated muscles which plays a role in myofibrillogenesis. Probably involved in the assembly of myosin into sarcomeric A bands in striated muscle (PubMed:11448995, PubMed:16205939). Has serine/threonine protein kinase activity and phosphorylates N-cadherin CDH2 and sodium/potassium-transporting ATPase subunit ATP1B1 (By similarity). Binds (via the PH domain) strongly to phosphatidylinositol 3,4-bisphosphate (PtdIns(3,4)P2) and phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P2), and to a lesser extent to phosphatidylinositol 3-phosphate (PtdIns(3)P), phosphatidylinositol 4-phosphate (PtdIns(4)P), phosphatidylinositol 5- phosphate (PtdIns(5)P) and phosphatidylinositol 3,4,5-trisphosphate (PtdIns(3,4,5)P3) (PubMed:28826662). {ECO:0000250|UniProtKB:A2AAJ9, ECO:0000269|PubMed:11448995, ECO:0000269|PubMed:16205939, ECO:0000269|PubMed:28826662}.