Introduction to Proteins

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Introduction to Proteins

• Melissa Kosinski-Collins
• HHMI High School Field Trip March 30th and 31st

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What is a protein?

• A protein is a linear chain of amino acids
• 20 species of amino acid, properties dictated by
  side chain (R)
• Polar (hydrophillic) contain O and N
• Nonpolar (hydrophobic)
• Acidic negative charge
• Basic positive charge

CH
NH3
COO-
R
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What do proteins do?

• A protein has many occupations in the cell
• Structure and movement collagen, actin,
  tropomyosin
• Catalytic Activity lysozyme, DNase, metabolic
  pathway proteins
• Binding and Transport porin, hemoglobin
• Gene Regulation NFKB, transcription factors
• Replication ribosomal proteins, polymerase
• A proteins function is dictated by its shape!

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Hemoglobin
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Protein Composition

• Proteins are composed of amino acids covalently
  linked via polypeptide bonds

Peptide Bond
Amino Acid Subunit
O
R
R
C
NH
C
C
NH
C
NH
C
NH
C
C
R
O
O
R
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Protein Composition
Peptide Bond
Amino Acid Subunit
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Protein Have Multiple Levels of Structure

• Primary
• Secondary
• Tertiary
• Quaternary

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Protein Have Multiple Levels of Structure

• Primary
• Linear sequence of amino acids
• Hemoglobin A Chain
• mghfteedka titslwgkvn vedaggetlg rllvvypwtq
  rffdsfgnls sasaimgnpk vkahgkkvlt slggaikhld
  dlkgtfaqls elhcdklhvd penfrllgnv lvtvlaihfg
  keftpevqas wqkmvtavas alssryh

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Proteins Have Multiple Levels of Structure

• Secondary
• a-helices, b-sheets, turns, and random coils
• Controlled by hydrogen bonding network

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Protein Have Multiple Levels of Structure

• Tertiary
• Interaction of pieces of secondary structure
• Controlled by side chain interactions

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Protein Have Multiple Levels of Structure

• Quaternary
• Interaction of multiple chains
• Interactions are controlled by shape and chemistry

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How Complex are Proteins?

• Use most amino acids
• No glaring order of amino acids
• Example Average E. Coli protein
• 300 a.a. long
• 20 possible a.a. at each position
• 20300 possible sequences (bigger than the number
  of atoms in the entire universe!)
• DNA structure is independent of sequence
• Protein structure change with sequence change

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Today

• Study the structure and function of hemoglobin
• Locate and examine the location of a hemoglobin
  mutation associated with Sickle Cell Anemia
• Determine what protein you are and assess its
  prevalence