The article by Theodore L. Steck reviews the organization of proteins in the human red blood cell membrane. It highlights the importance of the erythrocyte plasma membrane as a model for studying cell membrane structure and function. The review focuses on the localization and modes of association of major polypeptides within the membrane. Key points include: 1. **Membrane Preparation**: Red cell membranes can be isolated from hemolysed cells, and their composition is characterized by a high protein content (52%), followed by lipid (40%) and carbohydrate (8%). 2. **Protein Separation**: Proteins can be separated from lipids using polar organic solvents, with a small loss of protein content. The amino acid composition of the protein fraction shows an excess of acidic residues (21%) over basic residues (12%). 3. **Polypeptide Analysis**: SDS-gel electrophoresis is used to analyze the polypeptides in the membrane. The major polypeptides are identified and their molecular weights are estimated. The distribution of these polypeptides is asymmetric, with some spanning the membrane thickness. 4. **Asymmetrical Distribution**: The distribution of proteins on the outer and inner surfaces of the membrane is studied using various techniques, including exposure to nonpenetrating probes and resealing of ghosts. The results support the hypothesis of an absolute asymmetry in the distribution of proteins. 5. **Associations and Dissociations**: The association and dissociation of proteins in the membrane are explored using different methods, such as high ionic strength elution, low ionic strength elution, and protein perturbants. These studies reveal specific binding patterns and the selective solubilization of certain polypeptides. 6. **Electron Microscopy**: Electron microscopy is used to visualize intramembrane particles, which are believed to be composed of protein. The distribution of these particles is influenced by the presence of spectrin filaments. 7. **Phosphorylations**: The article discusses the phosphorylation of membrane proteins, particularly the acylphosphate intermediate of the Na⁺, K⁺-ATPase, and the role of cyclic AMP in phosphorylation. The review concludes with a summary of the topography of the major polypeptides in the human red blood cell membrane, emphasizing their asymmetric distribution and potential roles in various cellular functions.The article by Theodore L. Steck reviews the organization of proteins in the human red blood cell membrane. It highlights the importance of the erythrocyte plasma membrane as a model for studying cell membrane structure and function. The review focuses on the localization and modes of association of major polypeptides within the membrane. Key points include: 1. **Membrane Preparation**: Red cell membranes can be isolated from hemolysed cells, and their composition is characterized by a high protein content (52%), followed by lipid (40%) and carbohydrate (8%). 2. **Protein Separation**: Proteins can be separated from lipids using polar organic solvents, with a small loss of protein content. The amino acid composition of the protein fraction shows an excess of acidic residues (21%) over basic residues (12%). 3. **Polypeptide Analysis**: SDS-gel electrophoresis is used to analyze the polypeptides in the membrane. The major polypeptides are identified and their molecular weights are estimated. The distribution of these polypeptides is asymmetric, with some spanning the membrane thickness. 4. **Asymmetrical Distribution**: The distribution of proteins on the outer and inner surfaces of the membrane is studied using various techniques, including exposure to nonpenetrating probes and resealing of ghosts. The results support the hypothesis of an absolute asymmetry in the distribution of proteins. 5. **Associations and Dissociations**: The association and dissociation of proteins in the membrane are explored using different methods, such as high ionic strength elution, low ionic strength elution, and protein perturbants. These studies reveal specific binding patterns and the selective solubilization of certain polypeptides. 6. **Electron Microscopy**: Electron microscopy is used to visualize intramembrane particles, which are believed to be composed of protein. The distribution of these particles is influenced by the presence of spectrin filaments. 7. **Phosphorylations**: The article discusses the phosphorylation of membrane proteins, particularly the acylphosphate intermediate of the Na⁺, K⁺-ATPase, and the role of cyclic AMP in phosphorylation. The review concludes with a summary of the topography of the major polypeptides in the human red blood cell membrane, emphasizing their asymmetric distribution and potential roles in various cellular functions.