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Lecture 3

LECTURE 3.docx

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Steve Joordens

SLIDES FROM LECTURE 2SLIDE 63Specific linear sequence of amino acids This is dictated by mRNA which is dictated by the genen is the number of amino acids and it varies between proteins you can have short proteins or long proteins Primary sequence tells it all it tells how protein is going to fold where its going to go into the cell and once it gets there how it will functionSLIDE 64In sickle cell anemia the sickled blood cells clog up blood vessels and eventually burstYou get this from a change in the primary sequence of hemoglobin 1 amino acid is wrong which should be glutamic acid but instead its substituted for Valine due to a single point mutation one nucleotide is wrong in the geneWhy is the wrong amino acid brought in If theres a point mutation in the gene its going to go to mRNA and the wrong tRNA will come inPrimary sequence is critical not only for function of the protein but because it effects the entire cell alsoSLIDE 65Not all proteins have secondary structure It depends on the amino acid sequence if they have the correct amino acid sequence they will form secondary structure so it depends on the primary sequenceIf you have the appropriate stretch of amino acids they arrange to make maximum number of hydrogen bonds between the amino acidsTwo common types are alpha helix and beta pleated sheets zig zag configurationSLIDE 68All proteins have the 3D tertiary structureR groups that are hydrocarbon rich interact at a distance The interaction is hydrophobic These interactions help the protein fold and adopt its shapeIn the middle a hydroxyl group is interacting with an oxygen to form a hydrogen bond polar and at the bottom theres an ionic bond due to different chargesSLIDE 69You can see again the types of interactions between different R groups example disulfide bridge between cysteine R groupsSLIDE 70the 3D architecture results from intramolecular interactions the amino acids within the same protein are interacting this does not mean theyre close to one anotherTertiary structure can be visualized using Xray crystallographyThere are 2 categories of tertiary structures fibrous and globular proteinsSLIDE 71Fibrous proteins are typically proteins outside the cell They form long ropelike fibers example collagens These proteins resist pulling or shearing forces ECM is the extracellular matrixThese proteins are highly exploited in beauty industriesFibrous proteins are more rareSLIDE 72Most proteins have globular shapeSLIDE 73Most proteins dont fold naturally they need some assistance Chaperone proteins Hsp70 and chaperonin come to help the protein fold Hsp is called heatshock protein if you get a heatshock you might get denaturing so Hsp helps them fold properly Some proteins are so adversive in water that they go to chaperonin which is like a big barrel The new protein goes inside chaperonin so it can fold inside and be readyMisfolding is very common Things like Alzheimers and prions are caused by protein misfolding Adopting tertiary structure is important if you dont it leads to diseasesSLIDE 74When a protein is cleaved its hydrolyzed This can happen when proteins get to the right place and they get chopped up If its a nuclear protein its going to have a segment that will bring it into the nucleus once it gets there it doesnt need the segment so it gets chopped off
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