From Proteopedia
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The FpgNei Protein Superfamily
Functional Units
| G. Stereothermophilus Fpg
| E. Coli Nei
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| Functional Cluster | Variant 1 | Variant 2 | Fpg1 | Fpg2 | Plant | Neil1 | Neil2 | Neil3 | Proteo | Actino1 | Actino2 | MimiVirus
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| Support for perfectly conserved Asn168
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| Y | Y | N | N | N | N | N | N | N | N
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| Stability of catalytic helix
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| Y | Y | Y | N | N | N | N | N | N | N
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Functional Cluster 1: Stability of perfectly conserved Asn168
WebLogo for the first functional unit, note the covariation between lysine nad arginine, which support the crucial Asn174
Asn74, along with two other amino acids have an effect in the orientation and kinking of the DNA. In 4 of the 9 clades (Fpg1, Fpg2 and Plants and Fungi) Asn174 is supported by Lys160, which in turn hydrogen bonds with Leu249 and Ser250. In the other clades (Actinobacteria 1 and 2, Proteacteria and all vertebrate sequences), Arg171 that comes from a different helix fulfills the same roles as Lys160. One important difference is that the Zinc Finger is shaped differently in the absence of DNA, and there is a hydrogen bond between one of the beta-sheets and the arginine. One hypothesis is that the arginine or the lysine is necessary to support the Asn174, crucial for orientation of the DNA.
Functional Cluster 2: Stability of catalytic helix
The triad Leu4, Glu8 and Arg57 interact and provide stability to helixA, which has the catalytic residue Pro2,Glu3 and Glu6. This triad is present in the same four clades as above (Fpg1, Fpg2 and Plants and Fungi). This triad is not present in the remaining clades and it is not clear how the same stability is provided. Leu211 also has a hydrophobic interaction with Leu4.
Evolution
References
