lecture 3 062708 1p

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

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Unformatted text preview: 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 2 Review of Primary and Secondary structure Influenza Hemagglutinin Sequence of the amino acid residues Presence of alpha helices and beta sheets 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 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 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? 6 Protein Modifications 7 Protein modifications c These are often essential for the function of a protein and the regulation of protein activities: c Phosphorylation c Hydroxylation c Ubiquitination c Glycosylation c Proteolytic processing c Disulfide bond formation 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 9 Hydroxylation Hydroxyl groups can be added to lysine or proline 10 Glycosylation h Often occurs in the ER and secreted proteins h Addition of carbohydrates and can be added to Asp, Ser or Thr. residues 11 Ubiquitination: targets proteins for destruction Linked covalently to ubiquitin protein proteosome 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 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 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 15 GroEL-GroES assisted folding 16 Techniques in Protein Analysis 17 Protein Sequence Determination: Edman Degradation h It is useful to know the specific amino acid sequence of a...
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This note was uploaded on 07/12/2008 for the course LS 3 taught by Professor Lin during the Summer '06 term at UCLA.

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

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