SAM1 domain of SASH1 harbors distinctive structural heterogeneity

•This is the first structural study that characterizes a disordered SAM domain.•SAM diversity: SASH1-SAM1 is different from SASH3-SAM, a potential contributing factor for the diverse functions between SASH1 and SASH3.•Mutagenesis identified a way to shift between monomer and oligomer status of SAM1, providing a basis to target SAM1 for therapeutic strategy.•Higher compactness of region involved in dimerization may facilitate first encounter.