Table 2.
Intramolecular Hydrogen Bonds Stabilize the Substrate Conformation and Reduce the Km for hOGA
| TAB1 Peptide (Ser395) | p53 Peptide (Ser149) | |
|---|---|---|
| Original sequence | VPYS(O-GlcNAc)SAQ | QLVDS(O-GlcNAc)TPPPG |
| KM (hOGA) | 4,100 ± 300 μM | 21 ± 2 μM |
| Altered sequences | VPHS(O-GlcNAc)SAQ | QLVVS(O-GlcNAc)VPPPG |
| KM (hOGA) | 810 ± 140 μM | 3,700 ± 900 μM |
| QLVVS(O-GlcNAc)TPPPG | ||
| KM (hOGA) | 1,800 ± 200 μM |
The contribution of intramolecular hydrogen bonds toward substrate binding was probed by introducing a potential hydrogen bond donor in the sequence of the TAB1 peptide. For the p53 peptide, the hydrogen bond was disrupted by replacing either the donor or the acceptor with isosteric aliphatic amino acids (highlighted in boldface and underscored).