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首页> 外文期刊>Journal of Molecular Biology >HELIX PROXIMITY AND LIGAND-INDUCED CONFORMATIONAL CHANGES IN THE LACTOSE PERMEASE OF ESCHERICHIA COLI DETERMINED BY SITE-DIRECTED CHEMICAL CROSSLINKING
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HELIX PROXIMITY AND LIGAND-INDUCED CONFORMATIONAL CHANGES IN THE LACTOSE PERMEASE OF ESCHERICHIA COLI DETERMINED BY SITE-DIRECTED CHEMICAL CROSSLINKING

机译：现场定向化学交联法测定大肠埃希氏菌的乳糖通透中的螺旋邻近度和配体诱导的构象变化

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摘要

N and C-terminal halves of lactose permease, each with a single-Cys residue, were co-expressed, and crosslinking was studied. Iodine or N,N'-o-phenylenedimaleimide (o-PDM; rigid 6 Angstrom), crosslinks Asn245 --> Cys (helix VII) and Il52 --> Cys or Ser53 --> Cys (helix II). N,N'-p-phenylenedimaleimide (p-PDM; rigid 10 Angstrom) crosslinks the 245/53. Cys pair weakly, but does not crosslink 245/52, and 1,6-bis-maleimidohexane (BMH; flexible 16 Angstrom) crosslinks both pairs less effectively than o-PDM. Thus, 245 is almost equidistant from 52 and 53 by up to about 6 Angstrom. BMH or p-PDM crosslinks Gln242 --> Cys and Ser53 --> Cys, but o-PDM is ineffective, indicating that distance varies by up to 10 A. Ligand binding increases crosslinking of 245/53 with p-PDM or BMH, has little effect with o-PDM and decreases iodine crosslinking. Similar effects are observed with 245/52. Ligand increases 242/53 crosslinking with p-PDM or BMH, but no crosslinking is observed with o-PDM. Therefore, ligand induces a translational or scissors-like displacement of the helices by 3-4 Angstrom. Crosslinking 245/53 inhibits transport indicating that conformational flexibility is important for function. (C) 1997 Academic Press Limited. [References: 58]
机译：乳糖通透酶的N和C末端一半分别与一个Cys残基共表达，并研究了交联。碘或N，N'-邻苯二甲酰亚胺（o-PDM;刚性6埃），交联Asn245-> Cys（螺旋VII）和Il52-> Cys或Ser53-> Cys（螺旋II）。 N，N'-对苯二甲基亚胺（p-PDM;刚性10埃）交联245/53。 Cys对较弱，但不交联245 / 52，1,6-双马来酰亚胺己烷（BMH;柔性16埃）交联对对的有效性均不如o-PDM。因此，245与52和53的距离几乎相等，直至约6埃。 BMH或p-PDM交联Gln242-> Cys和Ser53-> Cys，但o-PDM无效，表明距离变化最多10A。配体结合增加了245/53与p-PDM或BMH的交联，对o-PDM几乎没有影响，并减少了碘的交联。 245/52观察到类似的效果。配体增加了与p-PDM或BMH的242/53交联，但没有观察到o-PDM的交联。因此，配体诱导螺旋平移或剪刀状移位3-4埃。交联245/53抑制了转运，表明构象柔韧性对功能很重要。 （C）1997 Academic Press Limited。 [参考：58]

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