EMP46 and EMP47 type 1 transmembrane proteins, N-terminal lectin domain
EMP46 and EMP47, N-terminal carbohydrate recognition domain. EMP46 and EMP47 are fungal type-I transmembrane proteins that cycle between the endoplasmic reticulum and the golgi apparatus and are thought to function as cargo receptors that transport newly synthesized glycoproteins. EMP47 is a receptor for EMP46 responsible for the selective transport of EMP46 by forming hetero-oligomerization between the two proteins. EMP46 and EMP47 have an N-terminal lectin-like carbohydrate recognition domain (represented by this alignment model) as well as a C-terminal transmembrane domain. EMP46 and EMP47 are 45% sequence-identical to one another and have sequence homology to a class of intracellular lectins defined by ERGIC-53 and VIP36. L-type lectins have a dome-shaped beta-barrel carbohydrate recognition domain with a curved seven-stranded beta-sheet referred to as the "front face" and a flat six-stranded beta-sheet referred to as the "back face". This domain homodimerizes so that adjacent back sheets form a contiguous 12-stranded sheet and homotetramers occur by a back-to-back association of these homodimers. Though L-type lectins exhibit both sequence and structural similarity to one another, their carbohydrate binding specificities differ widely.