Table 1.
Mutation positions for histidine-scanning library
| Number |
5 |
6 |
9 |
10 |
11 |
13 |
14 |
15 |
17 |
24 |
25 |
27 |
28 |
31 |
32 |
35 |
36 |
| Aminoacid residue of wild type |
F |
N |
Q |
Q |
N |
F |
Y |
E |
L |
E |
E |
R |
N |
I |
Q |
K |
D |
| Distance (Å) |
5.7 |
11 |
6.4 |
4.2 |
6.5 |
3.8 |
3.4 |
7.9 |
4.0 |
8.4 |
8.7 |
8.6 |
6.9 |
5.8 |
8.1 |
4.5 |
9.8 |
| fSASA (%) |
78 |
94 |
36 |
47 |
64 |
40 |
63 |
50 |
46 |
78 |
96 |
23 |
71 |
17 |
60 |
64 |
68 |
| Mixed codon used in the library |
YWT |
MAY |
CAW |
CAW |
MAY |
YWT |
YAT |
SAW |
CWK |
SAW |
SAW |
CRY |
MAY |
MWT |
CAW |
MAW |
SAT |
| Substituted amino acids in the library | H |
|
|
|
|
H |
|
H |
H |
H |
H |
|
|
H |
|
H |
|
| Y |
H |
H |
H |
H |
Y |
H |
D |
Q |
D |
D |
H |
H |
N |
H |
N |
H |
|
| L | L | Q | Q | Q | L | Q |
Distance in the table indicates the length between the PAB residue and the nearest positively charged residue in IgG-Fc. fSASA indicates the extent of solvent exposure of the side chain in wild-type amino acid residues of PAB. The seventeen mutation positions finally selected were classified into two groups: (1) the PAB residues were located within 9 Å from the positively charged IgG-Fc residues and (2) the PAB residues were located between 9 and 11 Å from the IgG-Fc residues, and with a fractional solvent-accessible surface area (fSASA) ((fSASA) = (SASA) (native)/SASA (denatured)) value of more than 68%. The following abbreviations are used for mixed bases: R = (A or G), Y = (C or T), M = (A or C), K = (G or T), S = (G or C) and W = (A or T). Substituted amino acid residues in the library indicate non-wild-type residues encoded by a mixed codon.