Umezu K, Chi N W, Kolodner R D
Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115.
Proc Natl Acad Sci U S A. 1993 May 1;90(9):3875-9. doi: 10.1073/pnas.90.9.3875.
The Escherichia coli RecF, RecO, and RecR proteins were analyzed for their effect on RecA-mediated pairing of single-stranded circular DNA and homologous linear duplex DNA substrates. As shown by other workers, joint molecule formation by RecA was inhibited by E. coli single-stranded DNA binding protein (SSB) when it was added to single-stranded DNA before RecA. This inhibitory effect was overcome by the addition of RecO and RecR or RecF, RecO, and RecR. Both the rate and extent of joint molecule formation were restored to the maximal level observed when SSB was added after RecA. RecF, RecO, and RecR proteins had no effect on the conversion of joint molecules to final products and only appeared to stimulate an early step in the pairing reaction. The stimulatory effect of RecF, RecO, and RecR was not seen without SSB or when SSB was added after RecA. RecF protein by itself inhibited reactions in mixtures containing RecA and SSB, and this inhibition was overcome by the addition of RecO and RecR. These data suggest that RecO and RecR, and possibly RecF, help RecA overcome inhibition by SSB and utilize SSB-single-stranded-DNA complexes as substrates.
分析了大肠杆菌RecF、RecO和RecR蛋白对RecA介导的单链环状DNA与同源线性双链DNA底物配对的影响。正如其他研究人员所表明的，当在RecA之前将大肠杆菌单链DNA结合蛋白（SSB）添加到单链DNA中时，RecA介导的联合分子形成受到抑制。添加RecO和RecR或RecF、RecO和RecR可克服这种抑制作用。联合分子形成的速率和程度都恢复到了在RecA之后添加SSB时观察到的最大水平。RecF、RecO和RecR蛋白对联合分子向最终产物的转化没有影响，似乎仅刺激配对反应的早期步骤。在没有SSB或在RecA之后添加SSB时，未观察到RecF、RecO和RecR的刺激作用。RecF蛋白本身会抑制含有RecA和SSB的混合物中的反应，添加RecO和RecR可克服这种抑制作用。这些数据表明，RecO和RecR，可能还有RecF，有助于RecA克服SSB的抑制作用，并将SSB-单链-DNA复合物用作底物。
