Table 1.
Intramolecular amide bonds determine length and protease resistance of BcpA pili
| BcpA mutant | Plasmid | Pili without trypsin |
Pili after 2.2 × 10−7 M trypsin |
||
|---|---|---|---|---|---|
| Length,* μm | P value† | Length,* μm | P value† | ||
| Wild type | pJB12 | 1.45 (0.52) | — | 1.41 (0.57) | — |
| Asn163Ala | pJB109 | 1.57 (1.02) | 0.63 | 1.00 (0.68) | 0.02 |
| Lys174Ala | pJB61 | 1.33 (0.50) | 0.47 | 0.18 (0.13) | 1.3 × 10−14 |
| Lys273Ala | pJB210 | 1.21 (0.37) | 0.10 | 0.38 (0.29) | 2.0 × 10−11 |
| Asp312Ala | pJB236 | 0.75 (0.31) | 1.2 × 10−5 | 0.07 (0.03) | 3.9 × 10−14 |
| Glu472Ala | pJB107 | 1.17 (0.51) | 0.07 | 0.45 (0.24) | 1.4 × 10−9 |
| Asn163Ala; Lys174Ala | pJB240 | 1.29 (0.89) | 0.60 | 0.19 (0.06) | 2.1 × 10−18 |
| Asn163Ala; Asp312Ala | pJB238 | 0.79 (0.19) | 8.0 × 10−6 | 0.06 (0.04) | 3.5 × 10−14 |
| Asn163Ala; Glu472Ala | pJB235 | 1.00 (0.36) | 0.002 | 0.29 (0.14) | 3.6 × 10−14 |
| Lys174Ala; Glu472Ala | pJB243 | 1.26 (0.58) | 0.25 | 0.16 (0.05) | 8.9 × 10−15 |
| Asn163Ala; Asp312Ala; Glu472Ala | pJB239 | 1.02 (0.33) | 2.7 × 10−3 | 0.10 (0.04) | 8.9 × 10−14 |
| Asn163Ala; Lys174Ala; Glu472Ala | pJB245 | 1.04 (0.49) | 0.09 | 0.19 (0.05) | 8.6 × 10−13 |
*Average pilus length measurement (n ≥ 20 immunoreactive particles) with the standard error of the mean in parentheses.
†Statistical significance was evaluated with the two-tailed homoscedastic Student's t test, and P values were recorded.