Hall S D, Kane M F, Kolodner R D
Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts.
J Bacteriol. 1993 Jan;175(1):277-87. doi: 10.1128/jb.175.1.277-287.1993.
Recombination of plasmid DNAs and recombination of bacteriophage lambda red mutants in recB recC sbcA Escherichia coli mutants, in which the recE region is expressed, do not require recA. The recE gene is known to encode exonuclease VIII (exoVIII), which is an ATP-independent exonuclease involved in the RecE pathway of recombination. A 33,000-molecular-weight (MW) protein was observed to be coexpressed with both exoVIII and a truncated version of exoVIII, pRac3 exo, when they were overproduced under the control of strong promoters. We have purified this 33,000-MW protein (p33) and demonstrated by protein sequence analysis that it is encoded by the same coding sequence that encodes the C-terminal 33,000-MW portion of exoVIII. p33 is expressed independently of exoVIII but is probably translated from the same mRNA. p33 was found to bind to single-stranded DNA and also to promote the renaturation of complementary single-stranded DNA. It appears that p33 is functionally analogous to the bacteriophage lambda beta protein, which may explain why RecE pathway recombination does not require recA.
在recB recC sbcA大肠杆菌突变体中，recE区域表达，质粒DNA的重组以及噬菌体λ red突变体的重组不需要recA。已知recE基因编码核酸外切酶VIII（exoVIII），它是一种参与RecE重组途径的不依赖ATP的核酸外切酶。当在强启动子的控制下过量表达时，观察到一种33,000分子量（MW）的蛋白质与exoVIII和exoVIII的截短版本pRac3 exo共表达。我们已经纯化了这种33,000-MW的蛋白质（p33），并通过蛋白质序列分析证明它由编码exoVIII C末端33,000-MW部分的相同编码序列编码。p33独立于exoVIII表达，但可能从相同的mRNA翻译而来。发现p33与单链DNA结合，也促进互补单链DNA的复性。似乎p33在功能上类似于噬菌体λβ蛋白，这可能解释了为什么RecE途径重组不需要recA。
