Fazakerley G V, Quignard E, Woisard A, Guschlbauer W, van der Marel G A, van Boom J H, Jones M, Radman M
EMBO J. 1986 Dec 20;5(13):3697-703. doi: 10.1002/j.1460-2075.1986.tb04702.x.
The Escherichia coli mismatch repair system does not recognize and/or repair all mismatched base pairs with equal efficiency: whereas transition mismatches (G X T and A X C) are well repaired, the repair of some transversion mismatches (e.g. A X G or C X T) appears to depend on their position in heteroduplex DNA of phage lambda. Undecamers were synthesized and annealed to form heteroduplexes with a single base-pair mismatch in the centre and with the five base pairs flanking each side corresponding to either repaired or unrepaired heteroduplexes of lambda DNA. Nuclear magnetic resonance (n.m.r.) studies show that a G X A mismatch gives rise to an equilibrium between fully helical and a looped-out structure. In the unrepaired G X A mismatch duplex the latter predominates, while the helical structure is predominant in the case of repaired G X A and G X T mismatches. It appears that the E. coli mismatch repair enzymes recognize and repair intrahelical mismatched bases, but not the extrahelical bases in the looped-out structures.
大肠杆菌错配修复系统并不能以同等效率识别和/或修复所有错配碱基对：虽然转换错配（G×T和A×C）能得到很好的修复，但一些颠换错配（如A×G或C×T）的修复似乎取决于它们在噬菌体λ异源双链DNA中的位置。合成了十一聚体并使其退火，以形成在中心有单个碱基对错配且两侧各有五个碱基对与λDNA已修复或未修复的异源双链相对应的异源双链。核磁共振（n.m.r.）研究表明，G×A错配会在完全螺旋结构和环出结构之间形成平衡。在未修复的G×A错配双链体中，后者占主导，而在已修复的G×A和G×T错配情况下，螺旋结构占主导。看来大肠杆菌错配修复酶能识别和修复螺旋内的错配碱基，但不能识别环出结构中的螺旋外碱基。
