Essential for the organization of sarcomeric actin thin filaments in skeletal muscle (PubMed:25774500, PubMed:26035871). Increases the rate of actin polymerization (By similarity). May interact with tropomyosin alpha (TPM1/2) N-terminus (By similarity). Interacts with KLHL40; leading to stabilization (PubMed:24960163). Highly expressed in nonstriated areas of developing myotubes, where it shows a granular cytoplasmic pattern. In sarcomeres, highly expressed in the M band region and, at lower levels, along actin thin filaments. Not detected in Z-disks. In sarcomeres, may be located near, but not at, actin thin filament pointed end. Skeletal muscle and heart-specific (at protein level). Expressed by 15.5 dpc in both skeletal muscle and heart. Expression is maintained throughout adulthood. Expression is regulated by SRF and MEF2. Ubiquitinated, leading to its degradation. Interaction with KLHL40 negatively regulates ubiquitination and degradation. Mice show severe muscle weakness and postnatal growth retardation. Skeletal muscles show the presence of nemaline bodies and have disorganized sarcomeric structures. Muscle atrophy is specific to the fast fibers. Belongs to the tropomodulin family. Extended N-terminus.