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lecture 3 062708 1p

lecture 3 062708 1p - Lecture 3 06.27.08 1 Brief review of...

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1 Lecture 3: 06.27.08 1. Brief review of Lecture 2 2. Protein folding/Protein modifications 3. Techniques in Analysis of Proteins - Sequencing - Purification - Detection
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2 Review of Primary and Secondary structure Influenza Hemagglutinin •Sequence of the amino acid residues •Presence of alpha helices and beta sheets
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3 Tertiary Structure Globular formation after all of the local structures are packed into place Domains of the protein, folds into appropriate confirmation in absence of the rest of the protein Can refer to them by structure or function. Ex: 1. DNA-binding domain leucine zipper 2. Transcription activation domain Domain may contain one or more motifs
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4 Quarternary Structure •Sub-unit structure of a protein •There are interactions that hold the sub-units together •Each polypeptide of a multimeric unit is called a subunit
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5 Different regions of a protein can be defined by function Binding site - reacts with another molecule through non-covalent interactions Dimerization region - where two different polypeptides interact with one another Active site - region where catalysis takes place Regulatory site - binding site for a molecule which may increase or decrease the activity of an enzyme Seeing the specific function of many sites on the protein, how does the cell ensure that proteins fold into their proper conformation?
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6 Protein Modifications
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7 Protein modifications checkbld These are often essential for the function of a protein and the regulation of protein activities: checkbld Phosphorylation checkbld Hydroxylation checkbld Ubiquitination checkbld Glycosylation checkbld Proteolytic processing checkbld Disulfide bond formation
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8 Protein phosphorylation •Addition of a phosphate group to the hydroxyl of serine, threonine, tyrosine and sometimes histidine •Protein phosphorylation/dephosphorylation provides a quick mechanism for altering protein activity
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9 Hydroxylation • Hydroxyl groups can be added to lysine or proline
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10 Glycosylation head2right Often occurs in the ER and secreted proteins head2right Addition of carbohydrates and can be added to Asp, Ser or Thr. residues
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11 Ubiquitination: targets proteins for destruction Linked covalently to ubiquitin protein proteosome
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12 Regulation via Protein Modification Kinase adds a phosphate group Phosphatase removes a phosphate group Adding or removing a phosphate can activate or inactivate a protein Phosphorylation can change conformation ligand binding site binding with another protein
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13 Example: Calmodulin 150 aa with 4 Ca ++ binding sites Typical cell has > 10 6 molecules Inactive Active Bound Intricate regulation: •addition/removal of phosphate group affects activity
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14 The role of molecular chaperones Facilitate proper folding in the cell Bind and stabilize partially or unfolded proteins and prevent interactions with other proteins
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15 GroEL-GroES assisted folding
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16 Techniques in Protein Analysis
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17 Protein Sequence Determination: Edman Degradation head2right
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