Receptor-like kinase involved in the control of pollen germination and pollen tube polar growth (PubMed:23024212, PubMed:24136420). Phosphorylates ROPGEF1 in its C-terminal region, releasing its auto-inhibition, and thereby activating the ROP1 signaling pathway (PubMed:23024212). May act as a scaffolding protein, recruiting ROPGEF12 to the plasma membrane by binding to its C-terminal domain (PubMed:18000057). Phosphorylates ROPGEF12, releasing its auto-inhibition (PubMed:18000057). ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] The phosphorylation activity is calcium-independent. Part of a complex containing ROPGEF1 and ARAC11/ROP1 (PubMed:23024212). The interaction between PRK2, ROPGEF1 and ARAC11/ROP1 is phosphorylation-independent (PubMed:23024212). Interacts with ROPGEF12 (via C-terminus)(PubMed:18000057). Interacts with ROPGEF1 (via PRONE domain)(PubMed:23024212). ROPGEF12 colocalizes with PRK2 at the apical plasma membrane of pollen tube. Expressed in pollen and/or in flowers, but not in leaves (PubMed:12139002). Expressed in pollen tube (PubMed:18000057). The protein kinase domain may be catalytically impaired due to the lack of the conserved Asp active site at position 466, which is replaced by a His residue. The juxtamembrane domain (274-319) is necessary for a relatively uniform plasma membrane localization. The C-terminal domain (614-647) is required for the induction of pollen tube depolarization. Both domains are required for the interaction of PRK2 with ROPGEF12. No effect on pollen germination and growth. Prk1 and prk2 or prk2 and prk5 double mutants have no effect on pollen germination and growth. Prk1, prk2 and prk5 triple mutant shows reduced pollen tube elongation. Belongs to the protein kinase superfamily. Ser/Thr protein kinase family.