A) protein anchored (B) protein anchored to membrane to membrane by a fatty acid chain C-C-O--CHa CH2 between terminal H一N mino group and s thioether linkage between cysteine fatty acid CYTOSOL C=o lipid 自 CH2"". (C) myristyl anchor Figure 10-14. The covalent attachment of either of two types of lipid groups can help localize a water-soluble protein to a membrane after its synthesis in the cytosol. (A)A fatty acid chain(either myristic or palmitic acid) is attached via an amide linkage to an amino-terminal glycine.(B)Aprenyl group(either farnesyl or a longer geranylgeranyl group- both related to cholesterol) is attached via a thioether linkage to a cysteine residue that is four residues from the carboxyl terminus. Following this prenylation, the terminal three amino acids are cleaved off and the new carboxyl terminus is methy lated before insertion into the membrane The structures of two lipid anchors are shown underneath: ( C)a myristyl anchor (a 14-carbon saturated fatty acid chain), and ( d) a farnesyl anchor(a 15-carbon unsatu hydrocarbon chair
Figure 10-14. The covalent attachment of either of two types of lipid groups can help localize a water-soluble protein to a membrane after its synthesis in the cytosol. (A) A fatty acid chain (either myristic or palmitic acid) is attached via an amide linkage to an amino-terminal glycine. (B) A prenyl group (either farnesyl or a longer geranylgeranyl group - both related to cholesterol) is attached via a thioether linkage to a cysteine residue that is four residues from the carboxyl terminus. Following this prenylation, the terminal three amino acids are cleaved off and the new carboxyl terminus is methylated before insertion into the membrane. The structures of two lipid anchors are shown underneath: (C) a myristyl anchor (a 14-carbon saturated fatty acid chain), and (D) a farnesyl anchor (a 15-carbon unsaturated hydrocarbon chain)
EXTRACELLULAR HIS (200) SPACE GLY SER ILE PHE ALA TYR GLY CYs GLY LEU ALA ALA GLY AL CYTOSOL (220)THR Figure 10-15. A segment of a transmembrane polypeptide chain crossing the lipid bilayer as an a helix. Only the a-carbon backbone of the polypeptide chain is shown, with the hydrophobic amino acids in green and yellow. J Deisenhofer et al. Nature 318: 618-624 and H. michel et al., EMB0. 5: 1149-1158)
Figure 10-15. A segment of a transmembrane polypeptide chain crossing the lipid bilayer as an a helix. Only the a-carbon backbone of the polypeptide chain is shown, with the hydrophobic amino acids in green and yellow. (J. Deisenhofer et al., Nature 318:618-624 and H. Michel et al., EMBO J. 5:1149-1158)
COoH Figure 10-17. A typical single-pass transmembrane protein. Note that the polypeptide chain traverses the lipid bilayer as a right-handed disulfide bonds a helix and that the oligosaccharides oligosaccharide chains and transmembrane a helix disulfide bonds are all on the noncytosolic surface of the membrane. Disulfide bonds do lipid bilayer not form between the sul fhydryl groups in the CYTOSOL sulfhydryl cytoplasmic domain of the reducing environment)//SHgroup protein because the reducing environment in the cytoso NH2 maintains these groups in their SH reduce d(-SH) form
Figure 10-17. A typical single-pass transmembrane protein. Note that the polypeptide chain traverses the lipid bilayer as a right-handed a helix and that the oligosaccharide chains and disulfide bonds are all on the noncytosolic surface of the membrane. Disulfide bonds do not form between the sulfhydryl groups in the cytoplasmic domain of the protein because the reducing environment in the cytosol maintains these groups in their reduced (-SH) form
hydrophobic a hydrophilic ead group Figure 10-18. a detergent micelle in water, shown in cross-section Because they have both polar and nonpolar ends, detergent molecules are amphipathic
Figure 10-18. A detergent micelle in water, shown in cross-section. Because they have both polar and nonpolar ends, detergent molecules are amphipathic
membrane protein detergent detergent in lipid bilayer micelles monomers ●● water-soluble protein soluble mixed lipid-detergent complex lipid-detergent micelles Figure 10-19. Solubilizing membrane proteins with a mild detergent. The detergent disrupts the lipid bilayer and brings the proteins into solution as protein lipid-detergent complexes. The phospholipids in the membrane are also solubilized by the detergent
Figure 10-19. Solubilizing membrane proteins with a mild detergent. The detergent disrupts the lipid bilayer and brings the proteins into solution as proteinlipid-detergent complexes. The phospholipids in the membrane are also solubilized by the detergent