Fig. 1: Biochemical and structural characterization of MTA1c.
From: Mechanism for the substrate recognition by a eukaryotic DNA N6-adenine methyltransferase complex
a Illustration of domain organization of Tetrahymena MTA1c components MTA1, MTA9/MTA9-B, p1 and p2. Abbreviations: CTD, C-terminal domain; CTR, C-terminal region; HLD, homeobox-like domain; HTH, helix-turn-helix; IR, insertion region; NH, N-terminal helices; NTD, N-terminal domain; NTR, N-terminal region. b Km and kcat values were calculated based on the MTase activities of MTA1cMTA9-B on two types of dsDNA in the presence of 20 μM SAM. For umDNA, the assay was performed in the presence of 1 μM MTA1cMTA9-B and 0–10 μM umDNA for 2 h at 30 °C. For hmDNA, the assay was performed in the presence of 0.125 μM MTA1c and 0–10 μM hmDNA for 0.5 h at 30 °C. Data are represented as mean ± SD from independent measurements (n = 3). c Kd values for MTA1cMTA9-B binding to DNA substrates were measured by fluorescence polarization experiments. 0–2 μM MTA1cMTA9-B was incubated with 1 nM 6-FAM-labeled umDNA or hmDNA. Data are represented as mean ± SD from independent measurements (n = 3). d Cryo-EM map of MTA1cMTA9-B in the apo state. e–g Cryo-EM structures of MTA1cMTA9-B in apo (e), SAH-bound (f), and SAM-bound (g) states. MTA1, MTA9-B, p1 and p2 are represented in a cartoon and colored green, cyan, slate and salmon, respectively. SAH and SAM are represented in magenta stick. h Cryo-EM structure of SAM-bound MTA1cMTA9-B with MTA1 D209A mutation. i Cryo-EM structure of SAM-bound MTA1cMTA9. MTA9 is colored dark cyan. j Structural comparison of MTA1c with MTA9 and MTA9-B. MTA9 and MTA9-B are aligned and zoomed in. Source data are provided as a Source Data file.
