Protein kinase involved in regulation of actin cytoskeleton organization and endocytosis. Phosphorylates the endocytic protein SLA1. The CDC28-CLN3 complex phosphorylation of SLA1 enhances its further phosphorylation by PRK1, weakening SLA1 association with PAN1, an activator of the actin-nucleating ARP2/3 complex. Plays a role in cell wall regulation and required for oxidative stress survival. ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Localized to sites of endocytosis. Leads to increased caspofungin sensitivity. Belongs to the protein kinase superfamily. Ser/Thr protein kinase family.