L Amino Acids Amino Acids are naturally found in L conformation Cystine Cysteine - when the amino acid is reduced (SH) *Hint: add electron so add an e in the name*Ĭystine - when the amino acid is oxidized (S) D vs.
The intracellular space is reducing (SH) because it contains antioxidants. In an oxidizing environment, the H's would be lost on the S's and the disulfide bridge can form.Įxtracellular portion of the cell is oxidizing so this is where these bonds will occur (S-S + no H anymore). It is an *alpha helix breaker* Why is Cysteine Special? These amino acids can form disulfide bridges.
Therefore, it disrupts secondary structure in proteins because it is so flexible. However, it is found a lot at the beginning of alpha helices Why is Glycine Special? This is the only non chiral amino acid. Why is Proline Special? Proline disrupts secondary structure in proteins as it induces more rigidity in the structure. This makes it useful to have in the *active site of a protein* where it can stabilize or destabilize a substrate. Because the pka is so close to to physiological pH, this will exist in protonated and deprotonated form. It uses an enzyme called protease to cleave a specific sectionĮg: Trypsin, chymotrypsin, cyanogin bromide Trypsin A protease that cleaves the C' terminus of amino acids K and R in peptide bonds Chymotrypsin A protease that cleaves the C' terminus of amino acids F, W, Y (hint: all aromatic groups) in peptide bonds Cyanogin Bromide A protease that cleaves the C' terminus of amino acid, M, in peptide bonds Special Amino Acids HistidineĬysteine Why is Histidine Special? The pka of Histidine's Nitrogen double bonded in the R group is 6.4. Proteolysis This is the specific cleavage of peptide bonds.
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