Structure-Based Demystification of Radical Catalysis by a Coenzyme B Dependent Enzyme-Crystallographic Study of Glutamate Mutase with Cofactor Homologues.

Catalysis by radical enzymes dependent on coenzyme B (AdoCbl) relies on the reactive primary 5'-deoxy-5'adenosyl radical, which originates from reversible Co-C bond homolysis of AdoCbl. This bond homolysis is accelerated roughly 10-fold upon binding the enzyme substrate. The structural basis for this activation is still strikingly enigmatic.

Structure-Based Demystification of Radical Catalysis by a Coenzyme B Dependent Enzyme-Crystallographic Study of Glutamate Mutase with Cofactor Homologues.

Catalysis by radical enzymes dependent on coenzyme B (AdoCbl) relies on the reactive primary 5'-deoxy-5'adenosyl radical, which originates from reversible Co-C bond homolysis of AdoCbl. This bond homolysis is accelerated roughly 10 -fold upon binding the enzyme substrate. The structural basis for this activation is still strikingly enigmatic.

Concomitant reconstitution of TraI-catalyzed DNA transesterase and DNA helicase activity in vitro.

TraI protein of plasmid R1 possesses two activities, a DNA transesterase and a highly processive 5'-3' DNA helicase, which are essential for bacterial conjugation. Regulation of the functional domains of the enzyme is poorly understood. TraI cleaves supercoiled oriT DNA with site and strand specificity in vitro but fails to initiate unwinding from this site (nic).

Extent of single-stranded DNA required for efficient TraI helicase activity in vitro.

The IncF plasmid protein TraI functions during bacterial conjugation as a site- and strand-specific DNA transesterase and a highly processive 5' to 3' DNA helicase. The N-terminal DNA transesterase domain of TraI localizes the protein to nic and cleaves this site within the plasmid transfer origin. In the cell the C-terminal DNA helicase domain of TraI is essential for driving the 5' to 3' unwinding of plasmid DNA from nic to provide the strand destined for transfer.