PTCD1 protein (Pentatricopeptide Repeat Domain 1) is a nuclear gene-encoded protein located in the mitochondrial matrix. Its core function lies in regulating mitochondrial gene expression and the assembly of the respiratory chain. It specifically recognizes and binds to mitochondrial RNA (such as mRNA or pre-RNA) through its characteristic pentapeptide repeat sequence (PPR) motif, participating in RNA processing, stability maintenance, or translation processes, thereby being crucial for the assembly and function of mitochondrial oxidative phosphorylation complexes (especially complex I). Its deficiency is associated with mitochondrial dysfunction, neurodegenerative diseases, and cardiomyopathy and other pathological processes.