Slide 23:Thermophiles also have proteins with fewer asparagines and glutamine,which are prone to breakdown via deamidation at high temperature. Slide 24:There are also extrinsic factors(factors external to the proteins themselves)that help to keep proteins stable.This slide shows 2-D gel analyses of proteins turned on at high temperature Some of these so called heat shock proteins are chaperones,a class of proteins that function by helped other proteins to stay properly folded.Some chaperones also help to refold denatured proteins Slide 25:Heat shock protein 60(hsp 60)is one major type of protein chaperone.It's mode of action is shown on this slide.This type of protein is important for helping proteins at both low temperature and at high temperature.The importance of protein chaperones to life at high temperature is highlighted by the fact that at the stressful high temperature of 108C up to 80% of the protein in the hyperthermophile Pyrodictium occultum consists of just one type of chaperone. Slide 26:There are also small organic molecules that can help to keep proteins folded at high temperature.You don't need to know the formulas but you do need to know the names of these molecules. Slides 27/28:DNA also needs to be stabilized at high temperature.This could be accomplished in theory by altering the GC content.G-C bonds are stronger than A-T bonds.However hyperthermophiles use proteins to stabilize DNA such as the histone-like protein Hmf.In addition,all hyperthermophiles use an enzyme called reverse gyrase to give their DNA a positive supercoil.Somehow positive supercoiling also confers greater thermal stability to the DNA Slides 29/30:Remember there are three domains to life,Bacteria,Eukarya and Archaea.Many hyperthermophiles belong within the domain Archaea and Archaea have very different types of membrane lipids.A single lipid molecule often contains four ether linkages.These confer more stability to the lipid chain than the two ester linkages used in Bacteria and Eukarya.The archaeal lipid chains also contain isoprene units that contain methyl groups sticking out from the plane of the hydrocarbon chain.These methyl groups also confer greater stability to the hydrocarbon.Slide 23: Thermophiles also have proteins with fewer asparagines and glutamine, which are prone to breakdown via deamidation at high temperature. Slide 24: There are also extrinsic factors (factors external to the proteins themselves) that help to keep proteins stable. This slide shows 2-D gel analyses of proteins turned on at high temperature. Some of these so called heat shock proteins are chaperones, a class of proteins that function by helped other proteins to stay properly folded. Some chaperones also help to refold denatured proteins. Slide 25: Heat shock protein 60 (hsp 60) is one major type of protein chaperone. It’s mode of action is shown on this slide. This type of protein is important for helping proteins at both low temperature and at high temperature. The importance of protein chaperones to life at high temperature is highlighted by the fact that at the stressful high temperature of 108ºC up to 80% of the protein in the hyperthermophile Pyrodictium occultum consists of just one type of chaperone. Slide 26: There are also small organic molecules that can help to keep proteins folded at high temperature. You don’t need to know the formulas but you do need to know the names of these molecules. Slides 27/28: DNA also needs to be stabilized at high temperature. This could be accomplished in theory by altering the GC content. G-C bonds are stronger than A-T bonds. However hyperthermophiles use proteins to stabilize DNA such as the histone-like protein Hmf. In addition, all hyperthermophiles use an enzyme called reverse gyrase to give their DNA a positive supercoil. Somehow positive supercoiling also confers greater thermal stability to the DNA. Slides 29/30: Remember there are three domains to life, Bacteria, Eukarya and Archaea. Many hyperthermophiles belong within the domain Archaea and Archaea have very different types of membrane lipids. A single lipid molecule often contains four ether linkages. These confer more stability to the lipid chain than the two ester linkages used in Bacteria and Eukarya. The archaeal lipid chains also contain isoprene units that contain methyl groups sticking out from the plane of the hydrocarbon chain. These methyl groups also confer greater stability to the hydrocarbon