Methionine sulfoxide reductase B3, also known as MSRB3, belongs to the methionine sulfoxide reductases (MSR) family proteins. MSRs are thought to protect against reactive oxygen species-induced oxidative damage in many organs, including the most environmentally exposed organ, human skin. MSRB3 plays an important role in cold tolerance by eliminating MetO and ROS that accumulate at the ER during cold acclimation.