Table 3. Structural comparison between HaBLA and nonhalophilic BLAs.
| -Lactamase | NQ-HaBLA (this work) | EaBLA (PDB entry 1zkj) | PfBLA (PDB entry 2qz6) | PaBLA (PDB entry 4nk3) |
|---|---|---|---|---|
| Biological source | Chromohalobacter sp. 560 | E. aerogenes (nonhalophilic) | P. fluorescens (nonhalophilic) | P. aeruginosa PAO1 (nonhalophilic) |
| Resolution () | 2.901.80 | 1.55 | 2.26 | 1.90 |
| No. of identified metal ion-binding sites | 8 | 7 | 0 | 0 |
| Sequence identity (%) | 100 | 48 | 48 | 48 |
| R.m.s.d. on C atoms () | 1.3 | 1.2 | 1.2 | |
| Volume† (3) | 55883 | 54351 | 54835 | 57986 |
| Acessible surface areas | ||||
| ASA (2) | 14093 | 13928 | 13941 | 14797 |
| ASA of nonpolar residues (2) | 4880 | 4831 | 4656 | 4658 |
| ASA of polar residues (2) | 9213 | 9097 | 9285 | 10140 |
| Amino-acid composition | ||||
| Nonpolar/polar residues‡ | 1.17 (198/169) | 1.23 (198/161) | 1.11 (188/170) | 1.19 (204/171) |
| Acidic residues (Asp + Glu) | 32 + 25 | 12 + 17 | 15 + 15 | 23 + 15 |
| Basic residues (Arg + Lys + His) | 18 + 9 + 5 | 13 + 18 + 10 | 5 + 23 + 9 | 24 + 16 + 6 |
| (Asp + Glu)/(Arg + Lys + His) | 1.78 | 0.71 | 0.81 | 0.83 |
| Solvent-accessible surface residues (ASA > 02) | ||||
| Nonpolar/polar residues‡ | 1.03 (162/157) | 1.07 (161/150) | 1.03 (156/152) | 1.03 (163/159) |
| Acidic residues (Asp + Glu) | 28 + 24 | 12 + 16 | 13 + 13 | 23 + 14 |
| Basic residues (Arg + Lys + His) | 17 + 9 + 5 | 13 + 17 + 10 | 5 + 22 + 9 | 24 + 12 + 6 |
| (Asp + Glu)/(Arg + Lys + His) | 1.68 | 0.70 | 0.72 | 0.88 |
| Density of negative charge (e2) | 1.49 103 | 0.86 103 | 0.72 103 | 0.34 103 |
†
The web-based program 3V was used for this calculation (Voss Gerstein, 2010 ▶).
‡
Nonpolar residues are Gly, Ala, Val, Leu, Ile, Pro, Phe, Met and Trp. Polar residues are Asp, Glu, Arg, Lys, His, Asn, Gln, Ser, Thr, Tyr and Cys.