A Structural Study on the Specificity of F1 Protease
Specificity studies of a thermostable alkaline serine protease F1 with its substrates were carried out through computational docking method. Structures of a series of synthetic peptide substrates were docked to the active site of the homology modelled F1 protease using AutoDock 3.0.5. The result...
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| Format: | Thesis |
| Language: | English |
| Published: |
2005
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| Subjects: | |
| Online Access: | http://psasir.upm.edu.my/id/eprint/5965/1/FBSB_2005_34%20IR.pdf |
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| Summary: | Specificity studies of a thermostable alkaline serine protease F1 with its
substrates were carried out through computational docking method.
Structures of a series of synthetic peptide substrates were docked to the active
site of the homology modelled F1 protease using AutoDock 3.0.5. The
resulting clusters of the substrates that were docked were analysed by
inspecting the energetic results and the orientation of each cluster to
determine the arrangement of productive binding. The amino acids of the
binding site that participated in the hydrophobic and hydrogen-bond
interactions were also determined. Docking results showed that all substrates
tested bound near the catalytic residues with SucAAPFpNA, the biggest
substrate, showing the most negative docked energy value @docked = -18.75
kcal/mol). Smaller substrates such as GpNA and AApNA showed higher
docked energy (Edocked = -7.77 kcal/mol and -8.77 kcal/mol, respectively). The
best docked structure of each substrate was determined from the clusters. It
was found that most of the lowest Edocked conformations display the best
docked orientations with respect to the least distance calculated between the
carbonyl carbon of the substrate PI residue and y-oxygen of the Ser226
catalytic triad. From the results, it also demonstrated that S1, S2 and S4
subsites of the enzyme play a critical role in determining the substrate
specificity of F1 protease from the point of view that bigger-sized substrates
such as SucAAPFpNA and SucAAPLpNA showed more favourable Edocked.
This work also support the hypothesis that the catalytic serine and histidine
residues were essential in catalysis as well as in stabilizing the enzymesubstrate
complex for binding.
Validation of computational study was carried out through biochemical
assay. It was found that SucAAPFpNA was the most preferred substrate for
the enzyme with specific activity of 3.079 U/mg followed by SucAAPLpNA
at 1.016 U/mg. SucAAPFpNA was also observed to show the highest binding
affinity towards the protease (Km = 1.26mM) and the highest catalytic ratio
(1.226 min-l.rnM-1) compared to the other substrates tested. Similar to
computational observations, smaller peptides showed lower specific activity
and binding affinity towards the protease. Rank-order of the substrates tested
for the docking and experimental methods were found to be similar for the
top two substrates, with lesser agreement for the other substrates. |
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