ATPB refers to the "ATP synthase, H+ transporting, mitochondrial F1 complex, beta polypeptide," which is a subunit of the mitochondrial ATP synthase enzyme. This enzyme is crucial for cellular energy production as it catalyzes the synthesis of ATP, utilizing the electrochemical gradient of protons across the inner mitochondrial membrane during oxidative phosphorylation. ATPB is one of the subunits that make up the F1 complex, the soluble catalytic core of ATP synthase, which is composed of five different subunits (alpha, beta, gamma, delta, and epsilon) assembled with a stoichiometry of 3 alpha, 3 beta, and a single representative of the other three. The protein is also known by several synonyms including ATP5B, ATPMB, ATPSB, and is associated with the gene symbol ATPB. The molecular weight of the protein is approximately 57 kDa, with a calculated molecular weight of 529 amino acids. ATPB plays a significant role in the process of ATP synthesis within the mitochondria, highlighting its importance in cellular metabolism and energy production.