Shibata T, Cunningham R P, DasGupta C, Radding C M
Proc Natl Acad Sci U S A. 1979 Oct;76(10):5100-4. doi: 10.1073/pnas.76.10.5100.
recA protein, which is essential for general genetic recombination in Escherichia coli, promotes the homologous pairing of single-stranded DNA with double-stranded DNA to form a D loop. The amount of recA protein required for the reaction was directly proportional to the amount of single stranded DNA and was unaffected by similar variations in the amount of double-stranded DNA. The ATP analog, adenosine 5'-O-(3-thiotriphosphate) (ATP gamma S), which was not rapidly hydrolyzed by recA protein, blocked the formation of D loops but promoted the formation of stable complexes of recA protein and single-stranded DNA. These complexes, in turn, bound homologous or heterologous double-stranded DNA and partially unwound it. Because ATP gamma S competitively inhibited the ATPase activity of recA protein (Km/Ki approximately 300), we infer that ATP gamma S binds at a site that overlaps the site for ATP and that the functional complexes formed in the presence of the analog probably represent partial steps in the overall reaction. If the complexes formed in the presence of ATP gamma S reflect natural intermediates in the formation of D loops, recA protein must promote homologous pairing either by moving juxtaposed single-stranded and double-stranded DNA relative to one another or by forming and dissociating complexes reiteratively until a homologous match occurs.
RecA蛋白对大肠杆菌的一般基因重组至关重要，它促进单链DNA与双链DNA的同源配对以形成D环。反应所需的RecA蛋白量与单链DNA量成正比，不受双链DNA量类似变化的影响。ATP类似物腺苷5'-O-(3-硫代三磷酸)(ATPγS)不能被RecA蛋白快速水解，它能阻断D环的形成，但能促进RecA蛋白与单链DNA形成稳定复合物。这些复合物继而结合同源或异源双链DNA并使其部分解旋。由于ATPγS竞争性抑制RecA蛋白的ATP酶活性（Km/Ki约为300），我们推断ATPγS结合在与ATP结合位点重叠的位点，并且在该类似物存在下形成的功能复合物可能代表整个反应中的部分步骤。如果在ATPγS存在下形成的复合物反映了D环形成过程中的天然中间体，那么RecA蛋白必定通过使并列的单链和双链DNA相对移动，或者通过反复形成和解离复合物直至发生同源匹配来促进同源配对。
