Table 1.
Molecular mass measurements of deoxynucleoside kinase subunits by MALDI and nanoelectrospray mass spectrometry
| Subunit | Sequenced N terminus | Calculated MH+* (no. of residues) | MALDI MH+ | Δ | Nanospray MH+ ± σ | Δ |
|---|---|---|---|---|---|---|
| Native dCK† | MIVLSG ⋯ | 26,116‡ (222) | 26,138 | +22 | 26,122 ± 4.8 | +6 |
| Native dAK (I)† | MIVLSG ⋯ | 24,499§ (213) | 24,504 | +5 | 24,500 ± 2.3 | +1 |
| Native dGK¶ | TVIVLSG ⋯ | 26,185 (223) | 26,196 | +11 | ND | — |
| Native dAK (II)¶ | MIVLSG ⋯ | 24,499 (213) | 24,499 | 0 | 24,501 ± 1.7 | +2 |
| Recombinant dGK‖ | TVIVLSG ⋯ | 26,185 (223) | 26,194 | +9 | 26,187 ± 2.8 | +2 |
| Recombinant dAK (II)‖ | TVIVLSG ⋯ | 24,568 (214) | 24,561 | −7 | 24,568 ± 3.8 | 0 |
| Mutant dGK** | MIVLSG ⋯ | 26,116 (222) | ND | — | 26,125 ± 7.5 | +9 |
ND, not determined.
*
Assumes sequence deduced from gene is modified at N terminus as determined by Edman sequencing (see previous column).
†
From dAK (I)/dCK heterodimer of L. acidophilus R-26.
‡
Assumes sequence for dCK is same as for dGK, except at the N terminus (second column).
§
Assumes sequence for dAK (I) is the same as dAK (II).
¶
From dAK (II)/dGK.
‖
From recombinant dAK/dGK.
**
From mutant dGK/dGK homodimer.