ANALYSIS OF A NUCLEOPROTEIN COMPLEX - THE SYNAPTOSOME OF GAMMA-DELTA RESOLVASE

The gammadelta resolvase protein is one of a large family of transposo n-encoded site-specific recombinases. It performs recombination in a D NA-protein complex that contains 12 resolvase protomers and two copies of the 120-base pair DNA substrate, res (each with three binding site s for a resolvase dimer). A derivative of resolvase with altered DNA b inding specificity was used to show that the role of resolvase at site I, which contains the crossover point, differs from its role at the o ther two binding sites. The resolvase dimers that initially bind to si te I are the only ones that require the residue Ser10, essential for c atalysis of DNA breakage. In addition, these site I-bound dimers do no t use a specific interaction between dimers that is required elsewhere in the complex for synapsis of the res sites.