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Dieter Buyst1,2*, Vicky Gheerardijn2, Bjorn Van Gasse1, Jos Van den Begin2, Annemieke Madder2 & José C. MarBns1
1 NMRSTR, Department of Organic Chemistry, University of Ghent, Krijgslaan 281 S4, B-‐9000, Ghent, Belgium 2 OBCR, Department of Organic Chemistry, University of Ghent, Krijgslaan 281 S4, B-‐9000, Ghent, Belgium
(*e-‐mail: [email protected])
In the development of esterase like DNAzymes, recent advances in OBCR made the introducBon of amino acid-‐like side chain func8onali8es on the thymine base possible. The hydrophobic and chiral environment of a B-‐DNA helix is used as a new scaffold for the development of synthe8c enzymes. Both first generaBon, single hisBdine modified systems and second generaBon, double modified systems are subjected to a systemaBc study.
1. General concept & design
Towards DNA based esterases: uncovering Hoogsteen face regula8on of the pKaH of a tethered imidazole func8onality by
NMR and molecular dynamics
From melBng temperatures: • No loss of stability due to modificaBon • Increase in stability is dependent on posiBon of
modificaBon: T8ImH+ (+ 5-‐6°C)
0,0
0,2
0,4
0,6
0,8
1,0
1,2
5 6 7 8 9 10
δobs, norm
pH
T8ImH+
T6ImH+ T7ImH+ Building block
sT21ImH+
T8ImH+A21 7,17 ± 0,02
7,92 ± 0,04
8,13 ± 0,04
8,72 ± 0,02 8,88 ± 0,05
9,07 ± 0,02
References [1] Broo, K.S., et al., J. Am. Chem. Soc., 1997, 119(47), 11362-‐11372 [2] Wüthrich, K., NMR of Proteins And Nucleic Acids, 1986
Acknowledgements The 700MHz is part of the INMRF jointly operated by UGent, UA and VUB.
2. First glimpse of the pKaH regula8ng mo8f
• Solely for T8ImH+ there’s a clear set of nOe contacts to posiBon n+3 (A11-‐T18 base pair)
• T8ImH+A21 and sT21ImH+ prove that an AT base pair is tolerated as well as that the moBf is robust and sequence-‐independent
T-‐T mismatch A-‐T base pair
System WT T6ImH+ T7ImH+ T8ImH+ WT T8ImH+A21 sT21ImH+
Tm (°C) 48,6 ± 0,5 50,5 ± 0,2 50,1 ± 0,3 54,6 ± 0,1 59,0 ± 0,3 64,1 ± 0,6 59,4 ± 0,2
5’-GACCATTTGCAGCG-3’ 3’-CTGGTAATCGTCGC-5’
7
23
strand 1 è
ç strand 2
22
21
6 8
Template sequence = Wild Type
14#mer'B"DNA&double'helix'
Concerns:'• 'stability&&&• spectral&complexity&'
TIm =
versus T8ImH+ Hε2 – G19O6
Running average interval = 25
T7ImH+ Hδ1 – T21O4
Running average interval = 25
50ns of MD trajectory shows persistent H-‐bridging in T8ImH+ and close interproton contacts validated in nOe’s
~ 2 ns
T8ImH+
G19
Hε1
Star8ng structure
T8ImH+
TImH+ TIm + H+
Thermal stability
TImH+ pKaH study via 1H NMR
1H NMR pH BtraBon: follow ε1 and δ2
of the TImH+
O
OH
HO
N
NH
O
O
NH
OHN
NH
H
Hε1
δ2
F2 [ppm] 9.0 8.5 8.0 7.5
F1
[ppm
] 8
6
4
2
"T8 His" 11 2 "/Users/Dieter/Documents/NMR Data/NMR Data 700MHz"
F2 [ppm] 9.0 8.5 8.0 7.5
F1
[ppm
] 8
6
4
2
T7His 7 1 "/Users/Dieter/Documents/NMR Data/NMR Data 700MHz"
F2 [ppm] 9.0 8.5 8.0 7.5
F1
[ppm
] 8
6
4
2
"T8 His" 11 2 "/Users/Dieter/Documents/NMR Data/NMR Data 700MHz"
F2 [ppm] 9.0 8.5 8.0 7.5
F1
[ppm
] 8
6
4
2
T8HisA21 3 1 "/Users/Dieter/Documents/NMR Data/NMR Data 700MHz"
T8ImH+' T8ImH+A21' sT21ImH+
'T7ImH+'
Hε1'–'T21'CH3'
F2 [ppm] 9.0 8.5 8.0 7.5
F1
[ppm
] 8
6
4
2
T21modHis 2 1 "/Users/Dieter/Documents/NMR Data/NMR Data 700MHz"
F2 [ppm] 9.0 8.5 8.0 7.5
F1
[ppm
] 8
6
4
2
T21modHis 2 1 "/Users/Dieter/Documents/NMR Data/NMR Data 700MHz"
Diagonal'peak'
C7'H5'
T5'CH3''
T5'H2’'T5'H2”'
Hε1'–'Hδ2'
G6'H8'
T5'H1’'
T5'H3’'C7'H3’'
T5H6'
C20'H5'
T18'CH3'
T18'H2’'T18'H2”'
Hε1'–'Hδ2'
G19'H8'
T18'H1’'
T18'H3’'C17'H3’'
9.0' 9.0' 9.0'8.7'
2.0'
4.0'
6.0'
8.0'
Hε1'
Specific nOe contacts
22
7
6
23
18
11
5’-GACCATTTImHGCAGCG-3’ 3’-CTGGTAAT CGTCGC-5’
9
21
20
19
8
10
T8ImH+
sT21ImH+ 5’-GACCTGCA TTAGCG-3’ 3’-CTGGACGTImHAATCGC-5’
22
21
24
23
6
8 5
7
9
10
22
23
3. Molecular Dynamics 4. Applica8on of the mo8f in double modified systems
A-‐T base pair
System WT T6T8ImH+ T7T8ImH+
Tm (°C) 59,0 ± 0,3 65,0 ± 0,4 63,9 ± 0,3
Δ to WT -‐ + 6,0 + 4,9
Thermal stability
22
7
6
23
18
11
5’-GACCATImHTTImHGCAGCG-3’ 3’-CTGGTA AA CGTCGC-5’
9
21
20
19
8
10
T6T8ImH+
22
6
7
23
18
11
5’-GACCATTImHTImHGCAGCG-3’ 3’-CTGGTAA A CGTCGC-5’
9
21
20
19
8
10
T7T8ImH+
0,0
0,2
0,4
0,6
0,8
1,0
1,2
5 6 7 8 9 10
δobs, norm
pH
T8ImH+ T6ImH+
Building block
0,0
0,2
0,4
0,6
0,8
1,0
1,2
5 6 7 8 9 10
δobs, norm
pH
T7ImH+
Building block
T8ImH+
T6T8ImH+ T7T8ImH+
System pKaH Δ pKaH
T6T8ImH+ T6ImH+ 7,82 ± 0,07 -‐ 0,10
T8ImH+ 8,90 ± 0,05 ≈
System pKaH Δ pKaH
T7T8ImH+ T7ImH+ 6,96 ± 0,07 -‐ 0,96
T8ImH+ 8,70 ± 0,06 -‐ 0,20
• Increase in melBng temperature is consistent with presence of the pKaH regulaBng moBf for T8ImH+ in both systems
• Increase in melBng temperature is less pronounced with increasing vicinity of the
imidazole funcBonaliBes
• In both systems the T8ImH+ funcBonality shows an increased pKaH value due to the intact moBf • For the other TImH+ funcBonaliBes (T6 or T7ImH+) pKaH decreases with increasing proximity due to repulsive posiBve
charge interacBons