DIRECT OBSERVATION OF CATALYTIC HYDROGEN ATOMS IN A SERINE PPROTEINASE: SUBTILISIN/CI-2A COMPLEX AT 1.05 Å RESOLUTION
Wojciech R. Rypniewski1, Claus von der Osten2, Peter Oestergaard2, Miroslawa Dauter1 and Keith S. Wilson1
1 European Molecular Biology Laboratory (EMBL),
c/o DESY, Notkestrasse 85, D-22603 Hamburg, Germany
2 Novo Nordisk, Novo Alle, DK-2880 Bagsvaerd,
Denmark
The structure of Alcalase, a natural variant of subtilisin Carlsberg, in complex with the chymotrypsin inhibitor CI-2A, has been solved at 1.05 Å using synchrotron radiation.
The atomic resolution structure reveals details of the catalytic site of the enzyme primed for nucleophilic attack on the substrate. The positions of the catalytically important hydrogen atoms are clearly visible. This is the first atomic resolution structure of a serine proteinase showing all the active site hydrogens.
This enables us to review the proposed catalytic mechanism of serine proteinases in light of direct structural data.