nodulin MtN21 family protein. similar to unknown protein [Arabidopsis thaliana] (TAIR:AT1G25270.1); similar to Protein of unknown function DUF6, transmembrane [Medicago truncatula] (GB:ABD28596.1); contains InterPro domain Protein of unknown function DUF6, transmembrane; (InterPro:IPR000620)