Fig. 2: MtATPS and MtAPSK catalyse the first steps of the \({\mathbf{SO}}_{\mathbf{4}}^{{\mathbf{2-}}}\) reduction pathway.
From: Assimilatory sulfate reduction in the marine methanogen Methanothermococcus thermolithotrophicus
a, Top panel, reactions catalyzed by MtATPS and MtAPSK; Bottom panel, the specific activity of MtATPS and MtAPSK, determined via a coupled enzyme assay. ‘-’ indicates the absence of the indicated reactant. Data are presented as mean ± s.d. and individual values are shown as grey spheres (n = 3 replicates). b, MtATPS homodimeric structure in which one monomer is shown in light yellow surface and the other one in cartoon. c, Active site of MtATPS (yellow) superposed on the ATPS from Thermus thermophilus HB8 (PDB: 1V47, grey) containing the APS shown as balls and sticks with carbons coloured cyan. Residues involved in substrate binding are highlighted in sticks and only the ones from MtATPS are labelled. Hydrogen bonds between the ATPS from T. thermophilus and APS are represented as dashed lines. Nitrogen, oxygen, phosphorus and sulfur are coloured in blue, red, orange and yellow, respectively. d, Sequence conservation across ATPS homologues. e, MtAPSK homodimeric structure in which one monomer is shown in light orange surface and the other one in cartoon. The flexible loop illustrated by the dashed line could not be modelled. In all structures, the N and C termini are shown by a blue and red sphere, respectively. f, Sequence conservation across APSK homologues. For d and f, red bold residues are involved in substrate binding, while red and black stars are perfectly and well-conserved residues, respectively.
