Catalyzes the attachment of proline to tRNA(Pro) in a two-step reaction: proline is first activated by ATP to form Pro-AMP and then transferred to the acceptor end of tRNA(Pro). Can inadvertently accommodate and process cysteine. The misacylated Cys-tRNA(Pro) is not edited by ProRS. ATP + L-proline + tRNA(Pro) = AMP + diphosphate + L-prolyl-tRNA(Pro) Homodimer. Belongs to the class-II aminoacyl-tRNA synthetase family. ProS type 2 subfamily.