Which of the following is an example of a single-pass transmembrane protein?
Single-pass type I membrane protein topology illustrated by glycophorin A major sialoglycoprotein CD235a abundant about million copies per red cell. Gene GYPA encodes one hundred fifty amino acids including signal peptide nineteen residues removed cotranslationally. Extracellular domain seventy residues heavily O-glycosylated with fifteen O-linked tetrasaccharides NeuAc-alpha2-3Gal-beta1-3 GalNAc plus one N-linked complex glycan contributing sixty percent mass, terminal sialic acid provides negative zeta potential preventing aggregation and defines M and N blood group antigens recognized by anti-M anti-N antibodies. Transmembrane segment residues seventy three to ninety five forms nineteen residue alpha helix enriched leucine isoleucine valine with dimerization motif L75 IxxG79 V80 xxG83 V84 xxT87 allowing tight van der Waals packing and strong association measured minus twelve kilocalories per dimer widely studied for helix-helix energetics. Cytosolic tail thirty six residues acidic interacts with protein 4.1R linking to spectrin actin junction regulating lateral mobility. Unlike seven-pass GPCR and fourteen-pass Band 3, single-pass architecture simplifies biophysical and invasion studies as receptor for Plasmodium falciparum EBA-175.
Ref: Alberts et al., Molecular Biology of the Cell, 6th ed., Chapter 10, Single-Pass Proteins – Glycophorin.