Glycophorins are red blood cell membrane glycoproteins that

Glycophorins are red blood cell membrane glycoproteins that bear important blood-group antigens. Shown below is the primary sequence for glycophorin B which possesses a single transmembrane segment. (Blanchard et al., J. Biol. Chem. 262 (1987) 5808). Identify the likely \'transmembrane\' segment (provide residue number range) and, using proper terminology, justify your selection. Leu Ser Thr Thr Glu Val Ala Met His Thr Ser Thr Ser Ser Ser Val Thr Lys Ser Tyr 20 lle Ser Ser Gin Thr Asn Gly Glu Met Gly Gln Leu Val His Arg Phe Thr Val Pro Ala 40 Pro Val Val lle lle Leu lle lle Leu Ser Val Met Ala Gly lle lle Gly Thr lle Leu 60 Leu lle Ser Tyr Ser lle Arg Arg Leu lle Lys 71

Solution

Transmembrane proteins are made of hydrophobic amino acid residues because both the tail of double layered plasma membrane is hydrophobic. So from the given sequence, we can deduce the amino acids which might be the part of the transmembrane segment of the glycophorin protein. From residue number 41 i.e. from Proline till residue number 72 i.e. Isoleucine.