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BIOLOGY 2B03 (244)
Kim Dej (39)
Lecture 2

in classs lecture 2 - sept 16.doc

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McMaster University
Kim Dej

InClassLecture2-September16th2013 -1980s: studying initial symptoms like memory loss, unaware of your surroundings, feeling like your sleep waking -these diseases are fatal because of pneumonia, and the ability to respond to it -prion: infectious protein taht exits in two conformations, we already have one of them in our body -the same protein in different shape is fatal -left: prpc: found in our bodies in some of our cells -the infectious prion is on the right, the sc form -differences in the two structures: right has more beta sheets, and left has more helices -this protein when its the left shape is good, but when its in the right shape is bad Slide 3 -protein folding takes awhile, its always folding and unfolding until it gets to the most stable native conformation - which has the lowest energy -will take many intermediate conformations before the final structure -most of the times it will look like the protein on the bottom right -but that also depends on the environment of the cell, whether or not it interacts with other proteins or other substrates Slide 4 -secondary structures are not dependent on the variable side chains, but instead on the hydrogen bonds that form between the back bone -any sequence can adopt a beta sheet or alpha helix -once these structures are all put together and fold in its native conformation it reaches the tertiary structure -sometimes one protein is not enough, so it interacts with others, and then reaches quaternary structure -motifs: fit in the middle, and build up to make tertiary structures -motifs are collections of the secondary structure, they are the combinations of the alpha helices or beta sheets Slide 5 -we might see the same motif in different proteins -different sequences of proteins can form the same motif -pieces of those sequence will be for a specific motif slide 6 -one alpha helix and two beta strands (a mini beta sheet) -these three are positioned in relative to one another, and its very special -its held in position with the association of a zinc ion -the position of the zinc ion is determined by four amino acids - 2 cystine, and 2 histadine -the positions of these amino acids must be exact so they can form a cavity for the ion -you have to have three other amino residues in between the cystine and the histadine -the polypeptide sequence is determining t
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