Plays a role in the export of proteins that lack a signal peptide and are secreted by an alternative pathway. Binds two calcium ions per subunit. Binds one copper ion. Binding of one copper ion does not interfere with calcium binding. Required for the copper-dependent stress-induced export of IL1A and FGF1. The calcium-free protein binds to lipid vesicles containing phosphatidylserine, but not to vesicles containing phosphatidylcholine (By similarity). Homodimer. Part of a copper-dependent multiprotein complex containing S100A13, FGF1 and SYT1. Interacts with FGF1 and SYT1 (By similarity). Interacts with IL1A (By similarity). Secretion is mediated by exposure to stress and requires copper ions. Belongs to the S-100 family.