MCB 450 1st Edition Lecture 7 Outline of Last Lecture I. MonosaccharidesII. Glycosidic bondsIII. Polysaccharides Outline of Current Lecture I. Some Explanationsa. Glycoconjugatesb. Proteoglycansc. Glycoproteinsd. Glycan SynthesisII. Examples of Importance of Glycans Current LectureAsparagine-linked (N-) glycoproteins-Biosynthetic pathway is very highly conserved in eukaryotesOligosaccharide is built up on and transferred from a carrier lipid-Lumen -- interior of endoplasmic reticulum-7-14 slide -- missing diagramN-linked saccharides are trimmed further, and new sugars are added back in the Golgi-Golgi is the compartment that follows the endoplasmic reticulumN-linked glycans are important-If an asparagine is missing it leads to congenital defectsMucins are heavily O-glycosylated-Mucins -- long proteins that are very rich in serines and threonines, the hair-like projections are short O-linked chainsoMakes a rather stiff moleculeoVery hydratedoVery similar concept to the glycosaminoglycansoCoats various mucus membranes -- forms a gel like substanceContribution of carbohydrate to protein structure-If you took two sugars and expected them to automatically make a bond in a solution that wouldn't happen, the reaction is energetically unfavorableEnergetics of glycosidic bond formation-UDP-glucose -- nucleotide-Universal donors used in all factions of lifeThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.Nucleophiles and leaving groups-Activation by UDP is what makes it want to accept a reaction with a nucleophile-Cellulose most abundant polymer on the planetGlycosyltransferases can have inverting or retaining mechanisms-Exam questions -- expect to know that donor has an alpha-linked linkageInverting or retaining mechanism?-Glycogen synthase --Retaining-Cellulose synthase --InvertedCarbohydrate-protein interactions-Antibodies will recognize certain types of carbohydratesLectins-Lectins -- do not come from immune systemoCan distinguish between subtle differences in carbohydrate structuresoToxin will be attracted to the lectin that is present on a glycoprotein wall-Purple diamonds -- sialic acid-Hemagglutinin binds to sialic acids then will make it across the cell wall to infect the cell-Different subtypes of influenza are described by their different types of hemagglutinin and neuraminidaseoEx: H1N1-Different Hs and Ns define influenza virus A subtypesoH1N1: Spanish fluoH3N2: 1968 Hong Kong fluoH5N1: Bird fluThe castor bean toxin ricin has a lectin domain-Why you should not eat raw castor beansoCompound is extremely distructiveoBulgarian journalist was injected with ricin by an umbrella contraption in the 60sABO(H) blood group antigens-Straightforward genetic basis for blood type in humans-Type O -- mutation where it eliminates the transferase altogether Erythropoietin-Illustrates the importance of human physiology-EPO -- is a hormone and is normally produced in the kidney oWhere our body notices lower than normal levels of oxygen and then will secreteEPO into the blood streamoStimulates red blood cell production-EPO improves performance in endurance sportsoIncreases oxygen supply to musclesoUsed in long distance bicycle