TABLE 1

Lack of correlation between α-carbon distances in the crystal structures and ability of TonB Cys substitutions to form disulfide-linked dimers in vivo

ResidueDistance (Å)aDimer formationb
1IHR1U07
G18651.4 59.2 Strong
F2026.531.4 Strong
W21335.6 45.1 Strong
Y21547.0 51.4 Strong
L22920.7 25.1 -
F23012.6 (8.0) 19.4 (18.4) Strong
K2318.6 (7.2)13.6 (12.4) -
I2324.4 (3.7) 6.5 (2.7) -
N2338.1 (5.2) 5.7 (3.7)Weak
• a  Predicted distance between α-carbon atoms was calculated using the Swiss-PDBViewer, DeepView v4.0 (http://spdbv.vital-it.ch/).The distance between sulfur groups of optimized Cys rotamers is shown in parentheses. 1IHR and 1U07 are Protein Data Bank (PDB) identifiers for solved structures.

• b Relative levels of triplet dimer formation are shown in Fig. 1 and 2. A hyphen indicates that the dimers were relatively undetectable. The maximum distance between α-carbons of Cys residues that can form disulfide-linked dimers is ~7 Å (27). For a summary of similarities between the 1IHR and1U07 structures, see reference 24.