Med26_M is the middle domain of subunit 26 of Mediator. Med19 and Med26 act synergistically to mediate the interaction between REST (a Kruppel-type zinc finger transcription factor that binds to a 21-bp RE1 silencing element present in over 900 human genes) and Mediator.
Jiyao W et al.(2023). "The conserved domain database in 2023.",