Although the analogous variant in yeast appears to cause moderately reduced mismatch repair function, the human variant appears to have no functional impact (at least when the only variant in the protein) — no impact on interaction with MSH6, mismatch binding activities, or mismatch repair activity.
See Drotschmann K et al. 1999 (10469597), Liu WH et al. 2003 (12673796), Ollila S et al. 2008 (18470917).