Enables mitogen-activated protein kinase kinase binding activity. Predicted to be involved in intracellular signal transduction; regulation of MAP kinase activity; and regulation of cell population proliferation. Predicted to act upstream of or within positive regulation of MAPK cascade. Predicted to be part of protein-containing complex. Predicted to be active in endoplasmic reticulum and membrane. Human ortholog(s) of this gene implicated in breast adenocarcinoma. Orthologous to human KSR1 (kinase suppressor of ras 1). [provided by Alliance of Genome Resources, Apr 2022]