title: SMIM1 is a type II transmembrane phosphoprotein and displays the Vel blood group antigen at its carboxyl-terminus.
abstract: Disruption of SMIM1, encoding small integral membrane protein 1, is responsible for the Vel-negative blood type, a rare but clinically-important blood type. However, the exact nature of the Vel antigen and how it is presented by SMIM1 are poorly understood. Using mass spectrometry we found several sites of phosphorylation in the N-terminal region of SMIM1 and we found the initiating methionine of SMIM1 to be acetylated. Flow cytometry analyses of human erythroleukemia cells expressing N- or C-terminally Flag-tagged SMIM1, several point mutants of SMIM1, and a chimeric molecule between Kell and SMIM1 demonstrated that SMIM1 carries the Vel antigen as a type II membrane protein with a predicted C-terminal extracellular domain of only 3-12 amino acids.
authors.affiliation: Institut National de la Transfusion Sanguine, Paris FR 75015, France; Department of Biology, University of Vermont, Burlington, VT 05405, USA.
authors.forename: Lionel
authors.initials: L
authors.lastname: Arnaud
authors.affiliation: Department of Biology, University of Vermont, Burlington, VT 05405, USA.
authors.forename: Liam P
authors.initials: LP
authors.lastname: Kelley
authors.affiliation: Institut National de la Transfusion Sanguine, Paris FR 75015, France.
authors.forename: Virginie
authors.initials: V
authors.lastname: Helias
authors.affiliation: Institut National de la Transfusion Sanguine, Paris FR 75015, France.
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Cartron
authors.affiliation: Department of Biology, University of Vermont, Burlington, VT 05405, USA. Electronic address: bballif@uvm.edu.
authors.forename: Bryan A
authors.initials: BA
authors.lastname: Ballif
mesh_terms: D000595:Amino Acid Sequence; D001789:Blood Group Antigens / Q000737:chemistry* / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D005110:Extracellular Space / Q000378:metabolism; D057809:HEK293 Cells; D006801:Humans; D020014:K562 Cells; D008565:Membrane Proteins / Q000737:chemistry / Q000378:metabolism*; D008969:Molecular Sequence Data; D010750:Phosphoproteins / Q000737:chemistry / Q000378:metabolism*
chemical_list: D001789:Blood Group Antigens; D008565:Membrane Proteins; D010750:Phosphoproteins; C584052:SMIM1 protein, human
keywords: Blood group; Mass spectrometry; Phosphorylation; Small integral membrane protein; Type II membrane protein