nodulin MtN21 family protein. similar to integral membrane family protein / nodulin MtN21-related [Arabidopsis thaliana] (TAIR:AT1G43650.1); similar to unnamed protein product [Vitis vinifera] (GB:CAO14461.1); contains InterPro domain Protein of unknown function DUF6, transmembrane; (InterPro:IPR000620)