The S-adenosyl-L-methionine (SAM) hydroxide adenosyltransferase family groups several fluorinase and chlorinase enzymes whose common feature is that they mediate nucleophilic reactions of their respective halide ions to the C-5' carbon of SAM [<cite idref="PUB00054078"/>]. These enzymes utilise a rigorously conserved amino acid side chain triad (Asp-Arg-His) which may have a role in activating water to hydroxide ion. Structural studies indicate that the protein is a homotrimer, with each monomer being composed of N- and C-terminal domains [<cite idref="PUB00030772"/>, <cite idref="PUB00048880"/>]. The N-terminal domain has a central seven-stranded beta-sheet, which combines parallel and antiparallel strands sandwiched between alpha helices. The C-terminal domain forms a beta-barrel with a greek-key topology. SAM is bound at the interface between the C-terminal domain of one monomer and the N-terminal domain of the neighbouring monomer, with a total of three molecules bound by the trimer.This entry represents the C-terminal domain of these proteins. S-adenosyl-l-methionine hydroxide adenosyltransferase, C-terminal