Crucial component in meiotic recombination, functioning at some point after the initiation step of recombination. Plays a role in promoting the crossover outcome of meiotic recombination events. Required for formation of normal meiotic crossover, and crossover and chiasmata generated by artificially made DNA breaks. Together with him-14 and zhp-3 plays a role in the activation of DNA damage-dependent apoptosis at the DNA damage checkpoint in pachytene cells (PubMed:23832114). Heterooligomer of him-14 and msh-5 (By similarity). Interacts with the brc-1-brd-1 heterodimer (PubMed:30383754). From mid-pachytene, co-localizes with cosa-1 and rmh-1 at crossover sites of early recombination intermediates (PubMed:29521627, PubMed:30379819). Co-localizes with brc-1 at crossover sites in mid-late pachytene nuclei (PubMed:30383754). Expressed in the germline. Belongs to the DNA mismatch repair MutS family.