Table 1.

Properties of spin-labeled cysteine mutants of LacY

Spin-labeled mutantsNitroxide positionsNPGal binding* (relative to unlabeled mutant), %Distances modeled for apo LacY
Ca-Ca, ÅSpin – spin distances, Å
ShortLongAverage
R73C/S401C/WT Cytoplasmic ends of helices III and XII6941445248
R73C/S401C/C154G 93
R73C/Q340C/WT Cytoplasmic ends of helices III and X6336384843
R73C/Q340C/C154G 73
S136C/Q340C/WT Cytoplasmic ends of helices IV and X6234395145
N137C/Q340C/WT Cytoplasmic ends of helices IV and X9532304638
S136C /S401C/WT Cytoplasmic ends of helices IV and XII6040435549
N137C /S401C/WT Cytoplasmic ends of helices IV and XII5738335243
V105C/T310C/WT Periplasmic ends of helices IV and IX8034305040
V105C/T310C/C154G 94
I164C/T310C/WT Periplasmic ends of helices V and IX9727244133
I164C/T310C/C154G 88
I164C/S375C/WT Periplasmic ends of helices V and XI9433304538
  • *Detected by direct sugar-binding assay based on Trp-NPGal FRET as described in SI Materials and Methods .

  • Estimated using LacY crystal structure (PDB ID: 1PV6) as described in Materials and Methods.