S100 calcium-binding protein G (S100G)

S100 calcium-binding protein G (S100G), also known as calbindin-D9k, is a small cytosolic protein belonging to the S100 family of EF-hand calcium-binding proteins[3][2]. It is primarily expressed in the intestine, where its synthesis is vitamin D-dependent and correlates with enhanced intestinal calcium absorption[3]. S100G acts by buffering cytoplasmic Ca2+, thereby facilitating the ATP-dependent transport of calcium ions across the duodenal epithelium. Unlike some S100 proteins with prominent roles in disease or inflammation, S100G’s known function is largely restricted to calcium absorption and homeostasis in vitamin D-responsive tissues[3][2]. There is little evidence to support its candidacy as a direct therapeutic drug target or disease biomarker. S100G is not typically viewed as a therapeutic target (such as a receptor, enzyme, or transporter) and does not directly interact with drugs or serve as a biomarker. It differs from some other well-known S100 family proteins (e.g., S100B, S100A8/A9), which are involved in cancer, inflammation, or neurodegenerative diseases[4][5][1]. Its primary biological and physiological importance is in vitamin D–regulated intestinal calcium handling[3].

Other names

Protein S100-GCABP9KCALB3S100DCABPCABP1Calbindin-D9kVitamin D-dependent calcium-binding protein (intestinal)calbindin 3calbindin D9Kvitamin D-dependent calcium-binding protein (intestinal)