Functions in trans to edit the amino acid from incorrectly charged Cys-tRNA(Pro) via a Cys-tRNA(Pro) deacylase activity. May compensate for the lack of Cys-tRNA(Pro) editing by ProRS. Is also able to deacylate Cys-tRNA(Cys), and displays weak deacylase activity in vitro against Gly-tRNA(Gly), as well as, at higher concentrations, some other correctly charged tRNAs. Unlike some of its orthologs it is not able to remove the amino acid moiety from incorrectly charged Ala-tRNA(Pro). Non-essential gene. Has been suggested to be potentially involved in suppression of transcription of ushA. Reaction mechanism involves exclusion of catalytic water from the active site and substrate-mediated catalysis: the sulfhydryl side chain of the Cys substrate acts as a nucleophile and attacks the carbonyl center of the ester bond, leading to the cleavage of the Cys-tRNA ester bond and formation of a cyclic cysteine thiolactone intermediate. In contrast, the INS editing domain of ProRS catalyzes Ala-tRNA(Pro) hydrolysis via nucleophilic attack by a catalytic water molecule (PubMed:23185990). Belongs to the prolyl-tRNA editing family. YbaK/EbsC subfamily.