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The prosegment-subtilisin BPN' complex: crystal structure of a specific 'foldase'
T Gallagher1, G Gilliland, L Wang
1Center for Advanced Research in Biotechnology, University of Maryland Biotechnology Institute, Rockville, USA.
Structure (London, England : 1993)
|September 15, 1995
Summary
The bacterial protease subtilisin BPN
Area of Science:
- Biochemistry
- Structural Biology
- Enzymology
Background:
- Subtilisin BPN' (SBT) folding relies on its prosegment, which is autocatalytically removed.
- Mature SBT folds inefficiently without its prosegment, requiring catalysis for refolding.
- The prosegment facilitates the refolding of mature subtilisin.
Purpose of the Study:
- To elucidate the structural basis of prosegment-mediated folding catalysis in subtilisin BPN'.
- To understand the mechanism of prosubtilisin BPN' maturation and enzyme folding.
Main Methods:
- X-ray crystallography of the prosegment-SBT complex at 2.0 A resolution.
Main Results:
- The crystal structure reveals the prosegment as a compact domain binding SBT via extensive interfaces.
- The prosegment interacts with key enzyme surface helices and caps their N termini with negative charges.
- The prosegment C terminus occupies the enzyme's active site in a product-like conformation.
Conclusions:
- The complex structure supports a unimolecular cleavage mechanism for prosubtilisin BPN' involving N-terminal rearrangement.
- A folding catalysis mechanism is proposed where the prosegment stabilizes a folding nucleus.
- The N- and C-terminal subdomains of SBT may fold independently through propagation after nucleus formation.