Glycophorin amino acid sequence

Carbohydrate Structure and Amino Acid-Sequence Data for Glycophorin A,... 

The amino acid sequences for glycophorins A and A (see Refs. 8 and 19) are presented in Fig. 1. It may be clearly seen that residues 1-70 of these glycoproteins extend into the cell exterior. The hydrophobic portion of the glycoprotein, residues 71-92, appear to be imbedded in the phospholipid membrane, and residues 93-131 protrude into the cell cytoplasm. ... 

It may be noted that there appear to be two amino acid sequences for glycophorin one contains Leu and Glu at amino acid sequence positions 1, and 5, respectively, whereas the other contains Ser and Gly at amino... 

Fig. 1.—Amino Acid Sequence for Glycophorins and A. [Diamonds represent points of 0-glycosylation. The single N-glycosylation point occurs at Asn-26. The data were obtained from Refs. 8 and 19.]...

As mentioned earlier, glycophorin B carries the N and the Ss blood-group antigens. It is known that the first 26 residues of the amino acid sequence are identical to those in the N-terminal portion of glycophorin A". Moreover, relative to glycophorin A, it has a shortened amino acid chain, comprising 35 amino acid residues at the C-terminus. It is also known to contain 4 lysine residues. 

Prohaska and coworkers61 isolated sialo- and asialo-glyco-octapeptides from glycophorin AM and AN, and recorded their 13C-n.m.r. spectra at 50.3 MHz. Their work will be discussed in relation to other 13C-n.m.r.-spectral studies of a synthetic pentapeptide that has the same amino acid sequence as the N-terminal portion of glycophorin AM (see later). 

On the basis of their amino acid sequences and hydropathy plots, many of the transport proteins described in this chapter are believed to have multiple membrane-spanning helical regions—that is, they are type III or type IV integral proteins (Fig. 11-8). When predictions are consistent with chemical studies of protein localization (such as those described above for glycophorin and bacteriorhodopsin), the assumption that hydrophobic regions correspond to membrane-spanning domains is much better justified. 

Figure 12.27 Locating the membrane-spanning helix of glycophorin. (A) Amino acid sequence and transmembrane disposition of glycophorin A from the red-blood-celI membrane. Fifteer) O-linked carbohydrate units are shown as diamond shapes, and an N-linked unit is shown as a lozenge shape. The hydrophobic residues (yellow) buried in the bilayer form a transmembrane a helix. The carboxyl-terminal part of the molecule, located on the cytoplasmic ydeof the membrane, is rich in negatively charged (red) and positively charged (blue) residues,...

Although glycophorin B contains the same O-linked oligosaccharides as glycophorin A, EBA-175 did not bind to it. Later, the reason for this would be shown to be that the binding of EBA-175 to glycophorin A is not solely determined by sialic acid residues but also requires specific amino acid sequences (Sim et ah, 1994). 

Fig. 1.4. Amino acid sequence of human erythrocyte glycophorin A (Tomita et al., 1978) with presumed intramembranous a-helical segment. 0 and < > indicate positively and negatively charged residues, respectively, and S indicates glycosylated residues. The N-terminus is Leu and the C-terminus Gin.

Tomita, M., Furthmayr, H., and Marchesi, V.T., 1978, Primary structure of human erythrocyte glycophorin A. Isolation and characterization of peptides and complete amino acid sequence. Biochemistry, 17 4756. 

Tomita, M., and Marches , V. T., 1975, Amino-acid sequence and oligosaccharide attachment sites of human erythrocyte glycophorin, Proc. Natl. Acad. Sci. USA 72 2964-2968. 

Because erythrocytes (red blood cells) do not contain any subcellular organelles (they are essentially a membranous sac for carrying hemoglobin) their plasma membrane is a convenient model system for studies of membrane structure as it can readily be isolated from other membranes and intracellular components. One of the major glycoproteins in the plasma membrane of erythrocytes is glycophorin A a 131 amino acid protein that was the first integral protein to be sequenced (see Topic B9). This revealed that the polypeptide chain of glycophorin consists of three domains ... 

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