UMP UDP-GalNAc Golgi membrane Antiporter UMP UDP-GalNAc GaINAc transferase Newl Transporter Pis Phosphatase P protein UDP UMP 百Gal UDP- Gal d GaINAc UMP UDP-Gal Antiporter Gal transferase A FIGURE 17-33 The antiport uptake of nucleotide sugars into Golgi cisternae. Both UDP-galactose (UDP-Gal) and UDP
5. O-linked oligosaccharides are also added within the GC Proteins can also be modified by the addition of carbohydrates to the side chain of aceptor serine and threnine residues within specific sequences of amino acids. In constrast to N-linked oligosaccharides, they are formed by the addition of one sugar at a time and usuall consist of only a few residues. First sugar added is usually N-acetylgalactosamine, to which other sugar can then be added. In some case. these sugars are be further modified by the addition of sulfate groups
5. O-linked oligosaccharides are also added within the GC. Proteins can also be modified by the addition of carbohydrates to the side chain of aceptor serine and threnine residues within specific sequences of amino acids. In constrast to N-linked oligosaccharides, they are formed by the addition of one sugar at a time and usually consist of only a few residues. First sugar added is usually N-acetylgalactosamine, to which other sugar can then be added. In some case, these sugars are be further modified by the addition of sulfate groups
a)O-linked oligosaccharides (b)N-linked complex oligosaccharides GIc NANA NANA NANA B(1→2) a(2→3) a(2→3) a(2→3) B(1→4) B(1→4) B(1→4) Amino Amino GICNAC GICNAc GIcNAc acid Hyl Collagen Man NANA NANA a(2→3) a(2→6) B(1→4) 6(1→3) Gal GaINAc GICNAc B(1→4) GICNAC (6←1)∝ Amino Amino Se Glycophorin Amino Amino Asn acid NANA= N-Acetylneuraminic acid(sialic acid) Gal Galactose GaINAc= N-Acetylgalactosamine Man Mannose GIcNAc =N-Acetylglucosamine(conserved) Fuc Fucose GIcNAc= N-Acetylglucosamine
7.6 Membrane biosynthesis in the Er Membranes do not arise de novo, rather, they arise only from preexisting membranes. Newly synthesized proteins and lipids are continually being inserted into exsiting membranes, most of which occurs in the ER and membrane components move from the er to virtually every other compartment in the cell 1. Integral membrane proteins are synthesized, folded and processed on the RER and orientated in the ER membrane As mentioned above, newly synthesized polypeptides in the membrane and lumen of the. ER undergo a series of modifications or processes before they reach their final destinations. Chaprones, Calnexin and Calreticulin etc. several ER proteins promote correct folding of newly made proteins the formation and rearrangement of disulfide bonds and the rotation of peptidyl-prolyl bond
7.6 Membrane biosynthesis in the ER Membranes do not arise de novo, rather, they arise only from preexisting membranes. Newly synthesized proteins and lipids are continueally being inserted into exsiting membranes, most of which occurs in the ER and membrane components move from the ER to virtually every other compartment in the cell. 1. Integral membrane proteins are synthesized, folded and processed on the RER and orientated in the ER membrane As mentioned above, newly synthesized polypeptides in the membrane and lumen of the ER undergo a series of modifications or processes before they reach their final destinations. Chaprones, Calnexin and Calreticulin etc. several ER proteins promote correct folding of newly made proteins, the formation and rearrangement of disulfide bonds and the rotation of peptidyl-prolyl bond
And as they move along the GC cisterna stack, the glycosylation of proteins and lipids is carried out. Sugars are added by glycosyltransferases located in particular Golgi cisternae, and GAG chains are added to core proteins to form proteoglycans. Amino acids or the sugars modified, such as sulfation of sugars of proteoglycans and of selected tyrosines on the proteins And portions of the peptides may be removed to make it activated. Some proteins are assembled into multimeric complex. Topogenic sequences direct membrane proteins synthesized on the rer to assume their appropriate orientation in the ER membrane. Such orientation is retained during transport of a membrane protein with its res iding membrane to its final destination. The protein glycosylation is described as bellowing
And as they move along the GC cisterna stack, the glycosylation of proteins and lipids is carried out. Sugars are added by glycosyltransferases located in particular Golgi cisternae, and GAG chains are added to core proteins to form proteoglycans. Amino acids or the sugars modified, such as sulfation of sugars of proteoglycans and of selected tyrosines on the proteins. And portions of the peptides may be removed to make it activated. Some proteins are assembled into multimeric complex. Topogenic sequences direct membrane proteins synthesized on the RER to assume their appropriate orientation in the ER membrane. Such orientation is retained during transport of a membrane protein with its residing membrane to its final destination. The protein glycosylation is described as bellowing