May function as calcium sensor and contribute to cellular calcium signaling. In a calcium-dependent manner, functions by interacting with other proteins, such as EZR and PPP5C, and indirectly plays a role in physiological processes like the formation of microvilli in epithelial cells. May stimulate cell proliferation in an autocrine manner via activation of the receptor for activated glycation end products (RAGE). Homodimer and heterodimer with S100A1. Interacts with S100PBP and S100Z. Interacts with CACYBP in a calcium-dependent manner. Dimeric form binds to and activates EZR/Ezrin by unmasking its F-actin binding sites. Interacts with PPP5C (via TPR repeats); the interaction is calcium-dependent and modulates PPP5C activity. Colocalizes with S100PBP in the nucleus. Colocolizes with EZR in the microvilli in a calcium-dependent manner. Detected in all of the tissues except brain, testis and small intestine, expression level is higher in placenta, heart, lung, skeletal muscle, spleen and leukocyte. Up-regulated in various pancreatic ductal adenocarcinomas and pancreatic intraepithelial neoplasias. This protein binds two calcium ions. Belongs to the S-100 family. Sequencing error in Met-1 codon.