Table 2.
Analytical characterization of recombinant SpMTA and SpMTB and their independent constitutive fragments synthesized in (A) Zn- and (B) Cd-enriched media.
| MT | Concentration and metal/MT ratioa | ESI-MSb |
||
|---|---|---|---|---|
| Species (% abundance) | Theoretical MW | Experimental MW | ||
| A | ||||
| SpMTA | 3.2 × 10−4 M | Zn7-SpMTA (100) | 6976.1 | 6978.8 ± 0.9 |
| 6.1 Zn | Zn7S1-SpMTA (30) | 7010.2 | 7016.5 ± 2.5 | |
| Zn4-SpMTA (20) | 6786.0 | 6780.9 ± 0.2 | ||
| Zn3-SpMTA (20) | 6722.6 | 6715.9 ± 0.6 | ||
| αSpMTA | 0.9 × 10−4 M | Zn4-αSpMTA | 4127.5 | 4127.2 ± 0.1 |
| 3.8 Zn | ||||
| βSpMTA | 0.7 × 10−4 M | Zn3-βSpMTA (100) | 3010.3 | 3009.9 ± 0.1 |
| 2.3 Zn | Zn2-βSpMTA (30) | 2947.0 | 2943.8 ± 1.5 | |
| apo-βSpMTA (30) | 2820.2 | 2811.0 ± 1.3 | ||
| Zn1-βSpMTA (20) | 2883.6 | 2877.0 ± 1.2 | ||
| SpMTB | 2.3 × 10−4 M | Zn7-SpMTB (100) | 7144.4 | 7143.5 ± 0.5 |
| 5.2 Zn | Zn6-SpMTB (50) | 7081.0 | 7076.9 ± 1.3 | |
| Zn5-SpMTB (50) | 7017.6 | 7012.9 ± 1.1 | ||
| Zn4-SpMTB (60) | 6954.3 | 6944.0 ± 0.9 | ||
| Zn3-SpMTB (20) | 6890.9 | 6880.0 ± 1.4 | ||
| αSpMTB | 2.2 × 10−4 M | Zn4-αSpMTB | 4167.0 | 4166.1 ± 0.1 |
| 3.8 Zn | ||||
| βSpMTB | 0.8 × 10−4 M | Zn3-βSpMTB | 3139.5 | 3138.9 ± 0.1 |
| 3.1 Zn | ||||
| B | ||||
| SpMTA | 0.7 × 10−4 M | Cd7-SpMTA (100) | 7305.3 | 7304.5 ± 0.5 |
| 7.7 Cd | Cd7S1-SpMTA (20) | 7339.4 | 7341.6 ± 1.8 | |
| 0.0 Zn | ||||
| αSpMTA | 0.7 × 10−4 M | Cd4-αSpMTA | 4315.6 | 4316.1 ± 0.1 |
| 3.9 Cd | ||||
| 0.0 Zn | ||||
| βSpMTA | 0.2 × 10−4 M | Cd3-βSpMTA (100) | 3151.4 | 3151.8 ± 0.4 |
| 2.8 Cd | Cd3Zn1-βSpMTA (30) | 3214.8 | 3215.6 ± 0.6 | |
| 0.4 Zn | ||||
| SpMTB | 0.8 × 10−4 M | Cd8-SpMTB (100) | 7583.9 | 7584.1 ± 0.5 |
| 6.7 Cd | Cd7S2-SpMTB (50) | 7541.6 | 7534.4 ± 0.9 | |
| 0.0 Zn | Cd7-SpMTB (40) | 7473.5 | 7474.8 ± 0.4 | |
| αSpMTB | 1.3 × 10−4 M | Cd4-αSpMTB | 4355.1 | 4355.5 ± 0.4 |
| 4.0 Cd | ||||
| 0.0 Zn | ||||
| βSpMTB | 0.8 × 10−4 M | Cd3S2-βSpMTB (100) | 3348.7 | 3343.1 ± 0.5 |
| 2.9 Cd | Cd3-βSpMTB (40) | 3280.5 | 3280.8 ± 0.3 | |
| 0.0 Zn | ||||
a
MT concentration and metal/MT ratio calculated from acid ICP-AES results.
b
Experimental and theoretical molecular weights corresponding to the Zn- and Cd-peptides. Zn and Cd contents were calculated from the mass difference between holo- and apoproteins. Species shown in bold correspond to the major components of the preparations.