Rp-Adenosine-5'-O-(1-thiotriphosphate) (Rp-ATP-α-S), a sulfur-containing nucleotide derivative isomer and a purinergic P2Y1 receptor agonist, promotes calcium mobilization in HEK293 cells expressing the human P2Y1 receptor (EC50 = 75 nM). This compound exhibits binding affinity to washed isolated human platelets (Ki = 156 nM) and attenuates ADP-induced aggregation in human platelet-rich plasma (PRP; pA2 = 4.74), as well as inhibits cAMP production triggered by prostaglandin E1 (PGE1) in human PRP (pA2 = 5.26). Furthermore, it triggers relaxation in carbamoylcholine-constricted guinea pig taenia coli strips (EC50 = 56 nM). Rp-ATP-α-S also contributes to the synthesis of cyclic dinucleotides, recognized by bacterial riboswitches.