Human Reticulon 4 Interacting Protein 1 is a member of the medium chain dehydrogenase/ reductase (MDR) family. Riticulons are endoplasmic reticulum associated proteins involved in membrane trafficking and neuroendocrine secretion. The MDR/zinc-dependent alcohol dehydrogenase-like family, which contains the zinc-dependent alcohol dehydrogenase (ADH-Zn) and related proteins, is a diverse group of proteins related to the first identified member, class I mammalian ADH. MDRs display a broad range of activities and are distinguished from the smaller short chain dehydrogenases (~ 250 amino acids vs. the ~ 350 amino acids of the MDR). The MDR proteins have 2 domains: a C-terminal NAD(P) binding-Rossmann fold domain of a beta-alpha form and an N-terminal catalytic domain with distant homology to GroES.