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Circular dichroism spectroscopy and gel-filtration analysis were used in the investigation of the effects of various salts on the self-association of the RecA protein from Thermus thermophilus. Results reveal that self-association of this protein is strongly dependent on the type and concentration of the salt in solution. Monomeric proteins were also shown to bind to single-stranded DNA and exhibit an ATPase activity. The implications of these results are discussed.

Homologous recombination in Escherichia coli relies on the RecA protein which produces a helical nucleoprotein filament by polymerizing on the single-stranded DNA in the presence of ATP. The nucleoprotein filament's recognition of homology and its catalyzation of the strand exchange reaction is ill understood. A new study investigates the interaction of Escherichia coli with single-stranded DNA using fluorescence competition assay with 1-anilinonaphthalene-8-sulfonic acid (ANS). Results suggest that ANS binds to or close to the ATP-binding region.

A study was done on the role of Asp222 in the catalytic mechanism of Escherichia coli aspartate aminotransferase. It was shown that the presence of the negatively charged particle at position 222 is necessary for the withdrawal of the alpha-proton of the amino acid substrate and is responsible for the acceleration of the rate-limiting step by 5 kcal. mol(super -1). These results suggest that Asp222 serves as a protein ligand which binds the coenzyme within the active site and stabilizes the protonated N(1) of the coenzyme.

A combination of X-ray diffraction and other modular studies are conducted to determine the compounds that can act as the substrate specificity determinants of the methanogen homoaconitase (HACN) enzyme. The various mutations that can reverse the activity of HACN are also analyzed.

ADP-ribose pyrophosphatase (ADPRase) catalyzes the hydrolysis of ADP-ribose 5' -phosphate. The results state that interactions responsible for the substrate recognition are located at the terminal moieties of the substrate.

Previously by direct evolution, a mutant of kanamycin nucleotidyltransferase (KNT) was created. To what extent each mutation contributes to the increased stability is examined and the effects of mutations on the structure of KNT at 72 degree Centigrade using molecular dynamics simulations is analyzed.

The contribution of three kinds of hydrogen bonds to the conformational stability of a protein was estimated using systematic mutant proteins. Results showed that the contribution was 8.5 kJ/mol for a 3.0 angstrom long intramolecular hydrogen bond, 5.2 kJ/mol for a 3.0 angstrom long intermolecular hydrogen bond between the protein and water molecules, and 5.0 kJ/mol for a 3.0 angstrom long intermolecular bond between water molecules.

Research was conducted to determine the three-dimensional structures of pyridoxal 5'-phosphate-type aspartate aminotransferase (AspAT) from Thermus thermophilus HB8 and pyridoxamine 5'-phosphate type one in complex with maleate using X-ray crystallography at 1.8 and 2.6 angstroms resolution, respectively. Results indicate that the overall and the active site structures are essentially conserved between the AspATs of subroup Ia and the enzyme of subgroup Ib.