Molecular Characterisation of Titin N2A and Its Binding of CARP Reveals a Titin/Actin Cross-linking Mechanism

摘要: Abstract Striated muscle responds to mechanical overload by rapidly up-regulating the expression of cardiac ankyrin repeat protein, CARP, which then targets sarcomere binding titin N2A in I-band region. To date, role this interaction stress response remains poorly understood. Here, we characterise molecular structure CARP-receptor site (UN2A) and its CARP. We find that UN2A contains a central three-helix bundle fold (ca 45 residues length) is joined N- C-terminal flanking immunoglobulin domains long, flexible linkers with partial helical content. CARP binds engaging an α-hairpin UN2A, linker sequence, BC loop Ig81, jointly form broad interface. Mutagenesis showed CARP/N2A association withstands sequence variations use information evaluate 85 human single nucleotide variants. In addition, actin co-sedimentation, co-transfection C2C12 cells, proteomics on heart lysates, CARP-soaked myofibrils imply induces cross-linking myofilaments, thereby increasing myofibril stiffness. conclude acts as regulator force output preserves performance upon stress.