Position of glycoprotein polypeptide chain in the human erythrocyte membrane

Biosynthesis of Reticulocyte Membrane Proteins by Membrane-Free Polyribosomes

“…It is obvious that the sialoylglycoprotein in red cell membrane preparations is an authentic membrane protein, since it contains the A, B, and NM blood-group antigens found on the cell surface. Labeling studies showed that one other protein (molecular weight 100,000) is found at the cell surface (3,(8)(9)(10)(11)(12)). Bretscher showed further that different parts of these proteins are labeled by chemical reagents that act from the outside or the inside of the membrane (13, 14); hence, these proteins appear to span the membrane and must be considered authentic membrane proteins.…”

“…1, including labeled species B2 and E, is removed from the membrane during 10 min of incubation at 370 in either 0.5 M NaCl or in 0.1 mM EDTA (pH 8.0) (unpublished studies). Also (5,10,15, and 30 min) membranes from 0.4 ml of suspension (equivalent to 0.06 ml of packed cells) were isolated and analyzed by gel electrophoresis. Also, at 10 and 15 min 0.5 mg/ml of emetine was added to 0.4-ml aliquots of the cell suspension, and incubation was continued until 30 min, at which time membranes were isolated.…”

“…There exist 7-9 main components (1-8); the major species include two polypeptides of molecular weight greater than 200,000 (4), a protein of molecular weight 100,000, and a sialoylgylcoprotein which contains the MN, A, and B blood-group activities (8). The latter two species are the only membrane proteins found on the cell surface (3,(9)(10)(11)(12); they may also penetrate to the interior surface of the membrane (13)(14)(15). Little is known, however, about the biosynthesis of erythrocyte membrane proteins: the types of erythropoetic cells that synthesize each protein, the type of polysome (free or membrane-attached) that synthesizes the proteins, and the factors that regulate their synthesis.…”

Surface Proteins of the Erythrocyte Membrane Effect of Aging

“…It is clear that two classes of proteins are exposed to the outside of the intact human erythrocyte [7,14,15,21], These proteins could be iodinated by means of the enzyme lactoperoxidase; and a major part of these proteins could also be digested away by means of the streptococcal protease 'pronase'. The position of the bands suggested that the denaturable protein might be identical to one of these exposed proteins, and pronase digestion was utilized to test this assumption.…”

“…This analytical tool has allowed the identification of the protein components in membrane fractions and modified membranes. For example, it has been shown that the proteins which are easily solubilized by low ionic strength solvents have the extremely high subunit molecular weights of 220,000 and 240,000 [2], Similarly, the protein components having subunit masses of about 90,000-110,000 daltons have been shown to be accessible from the outside of the erythrocyte cell membrane [14,21], as is also true for the highest molecular weight glycoprotein [7,15]. The protein of subunit mass 33,000-35,000 daltons has been shown to be D-glyceraldehyde-3-phosphate: NAD oxidoreductase (phosphorylating), (EC 1.2.1.12) [1,20].…”