TABLE 1.
BtuB loop deletion variants
| Variant | Loopa
|
Deleted residues
|
Amt of BtuB protein (% of OM protein)b | ||
|---|---|---|---|---|---|
| Size (residues) | Position | Position | Sequence | ||
| Vector | NA | NAc | NA | 0 | |
| BtuB+ | NA | NA | NA | 46.1 ± 3.6 | |
| ΔL7-1 | 17 | 396-412 | 400-405 | QLYGFY | 47.3 ± 3.4 |
| ΔL7-2 | 17 | 396-412 | 406-410 | GNPNL | 40.4 ± 3.6 |
| ΔL8 | 15 | 439-452 | 444-448 | IDYDD | 47.6 ± 8.8 |
| ΔL9 | 8 | 488-497 | 494-499 | PLLRRA | 51.6 ± 8.4 |
| ΔL10 | 9 | 530-538 | 533-538 | SYPYQT | 39.1 ± 5.9 |
| ΔL11 | 15 | 567-581 | 572-580 | DYETVYGYQ | 44.2 ± 3.5 |
| Δnlfd | 15 | 567-581 | 567-570 | NLFD | 22.2 ± 1.2 |
a
The sizes and positions of the extracellular loops were determined from the crystal structure.
b
The amounts of BtuB in the outer membrane were estimated by densitometry of Coomassie blue-stained SDS-PAGE electropherograms of outer membrane proteins extracted from cells of strain RK5016 (ΔbtuB) carrying plasmid pAG1 derivatives expressing the different loop deletion variants. The amount of BtuB is expressed as a percentage of the intensity of staining of it and the major OM proteins.
c
NA, not applicable.