Homodimer and heterodimers. May be due to intron retention. Belongs to the Casparian strip membrane proteins (CASP) family. The predicted gene At4g16440 has been split into 3 genes: At4g16440, At4g16442 and At4g16444. The predicted gene At4g16440 has been split into 3 genes: At4g16440, At4g16442 and At4g16444.