Fig. 5: Functional determinants of sequence conservation in prokaryotic SAMHD1-like dNTPases.
a Cartoon representations of the SAMHD1 tetramer (PDB: 4BZC) and Dgt hexamer (PDB:4X9E). The two structures are shown such that the conserved secondary structure elements in one of the monomers (color-coded) are oriented the same way. b Census of HD-domain dNTPases in a database of complete prokaryotic chromosomes. The three numbers shown are the total number of identified SAMHD1-like dNTPases, Dgt-like dNTPases, and the total number of searched chromosomes, respectively. Each taxon is displayed linked to the time of its common ancestor with Gammaproteobacteria or Firmicutes93. c Sequence logo representations of multiple-sequence alignments for the SAMHD1-like and Dgt-like families of prokaryotic dNTPases. The secondary structure cartoons show the location of conserved secondary structure elements in the primary sequence of SAMHD1 and Dgt positioned above and below the secondary structure cartoons, respectively. Residues located within 5 Å of the active sites are colored green. Residues located within 5 Å of the allosteric ligands are colored red and orange in SAMHD1 and Dgt, respectively. Residues surrounding the SAMHD1 allosteric sites are also labeled. d Interactions of GTP and dCTP with the residues of the allosteric binding sites of SAMHD121 (PDB: 4TNP). e Interactions of the d(C*G*C*C*T) oligonucleotide with the allosteric sites (PDB:6U6X).
