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PDBsum entry 1s02
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Hydrolase (serine proteinase)
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PDB id
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1s02
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References listed in PDB file
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Key reference
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Title
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Effects of engineered salt bridges on the stability of subtilisin bpn'.
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Authors
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C.R.Erwin,
B.L.Barnett,
J.D.Oliver,
J.F.Sullivan.
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Ref.
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Protein Eng, 1990,
4,
87-97.
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PubMed id
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Abstract
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Variants designed using PROTEUS have been produced in an attempt to engineer
stabilizing salt bridges into subtilisin BPN'. All the mutants constructed by
site-directed mutagenesis were secreted by Bacillus subtilis, except L75K. Q19E,
expressed as a single variant and also in a double variant, Q19E/Q271E, appears
to form a stabilizing salt bridge based on X-ray crystal structure determination
and differential scanning calorimeter measurements. Although the double mutant
was found to be less thermodynamically stable than the wild-type, it did exhibit
an autolytic stability about two-fold greater under hydrophobic conditions. Four
variants, A98K, S89E, V26R and L235R, were found to be nearly identical to
wild-type in thermal stability, indicative of stable structures without evidence
of salt bridge formation. Variants Q271E, V51K and T164R led to structures that
resulted in varying degrees of thermodynamic and autolytic instability. A
computer-modeling analysis of the PROTEUS predictions reveals that the low
percentage of salt bridge formation is probably due to an overly simplistic
electrostatic model, which does not account for the geometry of the pairwise
interactions.
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