RecA enzyme

The recA enzyme does not catalyze any recombination event unless at least one free end of a single strand or a... 

The recombination process triggered by the initial scissions made by exoV and mediated by the recA enzyme are not sufficient for recombination between interacting chromosomes. An additional enzyme, resolvase, is required for efficient separation of the recombining chromosomes in the recA-chromosome complex. This protein is encoded by the ruvC gene in E. coli and is absolutely required for homologous recombination in the bacterium. Its effectiveness has also been demonstrated in a cell-free in vitro system. 

Incidentally, the fact that the recA enzyme carries two enzyme activities, one for homologous recombination and... 

Enzymes that promote various steps of homologous recombination have been isolated from both prokaryotes and eukaryotes. In E. coli, the recB, recC, and recD genes encode the RecBCD enzyme, which has both he-licase and nuclease activities. The RecA protein pro-... 

FIGURE 25-37 Models for recombinational DNA repair of stalled replication forks. The replication fork collapses on encountering a DNA lesion (left) or strand break (right). Recombination enzymes promote the DNA strand transfers needed to repair the branched DNA structure at the replication fork. A lesion in a single-strand gap is repaired in a reaction requiring the RecF, RecO, and RecR proteins. Double-strand breaks are repaired in a pathway requiring the RecBCD enzyme. Both pathways require RecA. Recombination intermediates... 

In E. coli the synthesis of many enzymes involved in repair is regulated by the so-called SOS system. Two proteins, lexA and recA, form the working machinery of this regulatory system (fig. 26.19). Under normal conditions the lexA protein inhibits the expression of about 17 genes (the din genes), the encoded proteins of which are... 

What is called DNA recombination repair is the replacement of a damaged segment of a DNA strand by a corresponding segment from an undamaged strand. In E. coli, at least, both these processes have been observed to be mediated or regulated by an enzyme (which is named RecA protein, and further identified as a 38-kDa nuclease). 

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