Schneider W P, Nichols B P, Yanofsky C
Proc Natl Acad Sci U S A. 1981 Apr;78(4):2169-73. doi: 10.1073/pnas.78.4.2169.
Hybrid tryptophan synthetase alpha and beta polypeptides were produced by genetic recombination between the trpB--trpA regions of Escherichia coli and Salmonella typhimurium contained on compatible, multicopy plasmids. Intragenic recombination was decreased but still evident in recA cells. Genetic exchange occurred at many sites within trpA, but every recombinant gene produced a functional alpha polypeptide despite many amino acid differences from one or the other of the parental polypeptides. The five hybrid tryptophan synthetase alpha subunits examined resembled the parental polypeptides in catalytic function but differed in thermostability. The stability differences suggest that, as amino acid changes occurred in these proteins during the course of evolution, subsequent changes were limited to those that would allow retention of a desired protein conformation.
通过位于相容多拷贝质粒上的大肠杆菌和鼠伤寒沙门氏菌的trpB-trpA区域之间的基因重组,产生了杂合色氨酸合成酶α和β多肽。在recA细胞中,基因内重组减少但仍然明显。基因交换发生在trpA内的许多位点,但每个重组基因都产生了一种功能性α多肽,尽管与亲本多肽中的一种或另一种有许多氨基酸差异。所检测的五个杂合色氨酸合成酶α亚基在催化功能上类似于亲本多肽,但在热稳定性上有所不同。稳定性差异表明,在进化过程中这些蛋白质发生氨基酸变化时,随后的变化仅限于那些能够保持所需蛋白质构象的变化。