TABLE 3

Properties of intragenic suppressors upstream of the C terminus

MutationBackgroundDoubling timea (min)Location in sequenceLocation in structure
Y32SL394A110bTM 1Cytoplasmic opening of pore
L35Ffs100bLoop 1Cytoplasmic opening of pore
G113CL394A, fs180,b 160bcTM 3Wall of pore opposite H168
V116F, LdL394A, K255A50TM 3Hydrophobic pockete
G117Wfs140bTM 3Cytoplasmic vestibule
A118EL394A100bTM 3Cytoplasmic vestibule
L119PdL394A60Loop 3Hydrophobic pockete
A120Pfs65Loop 3Cytoplasmic vestibule
F125LL394A180bLoop3Contact with adjacent monomer
W148LL394A, fs70, 55cTM 4Periplasmic opening of pore
V166Mfs55TM 5Periplasmic opening of pore
G175VL394A100bTM 5Near D310
A179EDouble, L394A, fs70, 70, 55cTM 5Near D310
A179SL394A, fs110, 85TM 5Near D310
A179Pfs110TM 5Near D310
R185Hfs140eLoop 5Multiple contactsf
P199Lfs120eTM 6Contact with adjacent monomer
G211S, Cfs80eTM 6Backbone contact with F215
R307Pfs140eLoop 9Near D310
C312Gfs60TM 10Cytoplasmic opening of pore
V314Ifs110eTM 10Cytoplasmic opening of poreg
I359Lfs70TM 11Lipid interface
  • a Minimal medium, pH 5.5, containing 0.5 mm Embedded Image and 0.1% glucose. Doubling times (min) of parental strains were the following: wild type, 50; amtB null, 200; ΔC-term, 110; double, L394A, and fs, 180 and increasing; K255A, 140 (Inwood et al. 2009).

  • b Initial doubling time. Doubling time increases as ammonium is consumed. See Figure 3.

  • c These doubling times correspond to the L394A and fs backgrounds, respectively.

  • d [14C]MA uptake values for V116L and F and L119P suppressors were 100% of wild type [100 pmol/(ml × OD600 × min)].

  • e Side chain is adjacent to a large hydrophobic pocket observed by Andrade et al. (2005).

  • f Contacts with other cytoplasmic loops and C terminus (see text, Figure 1B, and Inwood et al. 2009).

  • g Backbone contact with essential H318 in the pore.