Structure of inhibited trypsin from Fusarium oxysporum at 1.55 A.

The structure of trypsin from the fungus Fusarium oxysporum has been refined at 1.55 A resolution by restrained least-squares minimization to an R-factor of 14.4%. The data were recorded from a single-crystal on the X31 beamline at EMBL, Hamburg, using a locally developed image-plate scanner. The final model consists of 1557 protein atoms, 400 water molecules, one molecule of isopropanol and one monoisopropyl phosphoryl inhibitor group covalently bound to the catalytic Ser195. Comparison of the structure with bovine trypsin reveals significant differences in the active site and suggests a possible explanation for the difference in substrate specificity between the two enzymes. In F. oxysporum trypsin the specificity pocket is larger than in bovine trypsin. This explains the preference of F. oxysporum trypsin for the bulkier arginine over lysine and the reverse preference in bovine trypsin. The binding cavity on the C-terminal side of the substrate is more restricted in F. oxysporum trypsin than in mammalian and Streptomyces griseus trypsins, which explains the relative inactivity of F. oxysporum trypsin towards peptide-pNA substrate analogues as an unfavourable steric interaction between the side of the binding cavity and the para-nitroanilino group of peptide-pNA. The observed restriction of the binding cavity does not lead to a reduced catalytic activity compared to other trypsins.

Protein engineering of subtilisins to improve stability in detergent formulations.

Microbial proteases are used extensively in a large number of industrial processes and most importantly in detergent formulations facilitating the removal of proteinaceous stains. Site-directed mutagenesis has been employed in the construction of subtilisin variants with improved storage and oxidation stabilities. It is shown that in spite of significant structural homology between subtilisins subjected to protein engineering the effects of specific mutations can be quite different. Mutations that stabilize one subtilisin may destabilize another.

Molecular cloning, nucleotide sequence and fine-structural analysis of the Corynebacterium glutamicum fda gene: structural comparison of C. glutamicum fructose-1,6-biphosphate aldolase to class I and class II aldolases.

The Corynebacterium glutamicum fda gene encoding fructose-1,6-biphosphate (FBP) aldolase has been isolated by complementation of an Escherichia coli mutant. The nucleotide sequence of a 3371 bp chromosomal fragment containing the C. glutamicum fda gene was determined. The N-terminal amino acid sequence of C. glutamicum FBP aldolase identified the correct initiation site for the fda gene, and a molecular weight of 37,092 was predicted for the fda polypeptide. S1 nuclease mapping identified the transcriptional start site, and Northern hybridization analysis indicated that the fda gene encodes a single 1.3 kb transcript. The primary structure of C. glutamicum FBP aldolase shows strong homology to class II FBP aldolases. Conservation of primary structure was observed between class I and class II aldolases, but several residues essential for catalytic activity in class I aldolases were absent from class II aldolases.