9.B.384. The Small Integral Membrane Protein 1 (SMIM1) Family
The Vel blood group antigen is carried on the short extracellular segment of the 78-amino-acid-long, type II transmembrane protein SMIM1 of unknown function. Using cells expressing wild-type and mutant alleles of SMIM1, Kelley et al. 2019 demonstrated that dimerization of SMIM1 promotes cell surface display of the Vel epitope. SMIM1 dimerization is mediated both by an extracellular Cys77-dependent, homomeric disulfide linkage and a GxxxG helix-helix interaction motif in the transmembrane domain. These observations provide important context for the observed variability in reactivity patterns of clinically important anti-Vel identified in patient sera.