a, Model of the evolution of the gene encoding the TMAO-generating enzyme flavin monooxygenase 3. b, A maximum-likelihood tree and alignment of fish hsp90 sequences within five clades. Amino acids unique to the MHS are highlighted in red. c, Three-dimensional views of the hsp90 protein (hadal12091 is shown as an example; others are shown in Supplementary Fig. 36), highlighting MHS-specific amino acid substitutions. The homology model of the overall amino acid sequence is shown to the left; Ser202 atoms (coloured cyan) are shown as spheres. The expansion shows a model of the N-terminal domain, with the ligand-binding pocket coloured orange and shown in surface mode.