Structure of the recA protein-ADP complex.

Area of Science:

• Molecular Biology
• Biochemistry
• Structural Biology

Background:

• The recA protein is crucial for DNA repair and recombination, functioning as an allosteric enzyme.
• Its ATPase activity is DNA-dependent, with ATP binding increasing DNA affinity and ADP binding decreasing it.
• The precise role of ATP hydrolysis in recA's function remains unclear.

Purpose of the Study:

• To elucidate the structural basis of ADP binding within the recA protein crystal.
• To understand the mechanism of allosteric regulation of DNA binding by ATP.
• To compare the nucleotide-binding mechanism of recA with other NTPases.

Main Methods:

• X-ray crystallography to determine the atomic structure of recA with bound ADP.
• Biochemical assays to study DNA binding and ATPase activity.
• Structural comparison with known nucleotide-binding proteins.

Main Results:

• The bound ADP phosphates interact similarly to those in other NTPases with the conserved G/AXXXXGKT/S motif.
• A structural model suggests recA protein undergoes conformational changes upon ATP hydrolysis.
• This mechanism is analogous to the p21 protein from the ras oncogene.

Conclusions:

• ATP hydrolysis likely drives the transition of the triple-stranded DNA intermediate to products.
• The allosteric stimulation of DNA binding by ATP is explained by a conformational change model.
• The mechanism of coupling nucleoside triphosphate hydrolysis to ligand binding in recA may be conserved among related NTPases.