Biochemistry I   Spring & Fall Terms

Three Serine Protease Structures Superimposed


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  A. Display Model:
  1. Trypsin, only
      + Chymotrypsin
      + Elastase
  2. Chymotrypsin, only
      + Elastase
  3. Elastase, only
  All Three
      Differences (<1.5Å)

  B. Active Site Triads:
  Trypsin
  Chymotrypsin
  Elastase
  All Three

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The Architecture of Serine Proteases is Very Similar & their Active Sites are Nearly Identical
The initial model is trypsin (shown using the Backbone display with disulfide bonds colored yellow).
A. The first set of Display buttons superimpose the models of chymotrypsin or elastase in pairwise combinations or all three at once. Each chain can be selected individually using the Chime menu under "Model".
When two or three models are displayed, the residues in chymotrypsin and elastase that are <1.5Å from the trypsin structure are colored white by hitting the "Differences" button. The backbone architectures are very similar except for some loops and chain termini. Greater differences occur in the side chains. (Use the Sticks display to view these.) When the amino acid sequence of trypsin is aligned with those of chymotrypsin and elastase, the amino acids are identical at only 45% and 39% of the positions, respectively.

B. The second set of Display buttons zoom in to the active site, or "catalytic triad", residues found in all three enzymes (residue numbers differ for elastase). The three side chains are shown Ball & Stick, colored CPK, when viewed separately.
When all three are shown, the Display is Sticks; the colors are those used above for each enzyme (Chain colors).

Back to the Protein Structure List or the Rainbow Diagrams.

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8.21.04