Sam50 (sorting assembly machinery component 50 homolog, S. cerevisiae), also known as SAMM50, OMP85, TOB55, TRG-3, CGI-51 or YNL026W, is a β-barrel multi-pass membrane protein that belongs to the SAM50/omp85 family of proteins. Localizing to the mitochondrion, Sam50 is believed to function in the assembly pathway of mitochondrial outer membrane β-barrel proteins. More specifically, Sam50 functions as the major component of the SAM (sorting and assembly machinery) complex, also known as the TOB (topogenesis of mitochondrial outer membrane β-barrel proteins) complex, and is required for cell viability. Exposed to the intermembrane space (IMS), the N-terminal POTRA (polypeptide transport-associated) domain of Sam50 (a domain that is conserved from bacteria to man) functions like a receptor for β-barrel proteins. The association of the Sam35 subunit of the SAM complex is essential for Sam50 binding to outer membrane substrate proteins.