Abstract
The crystal structure of the conserved hypothetical protein Rv2991 from Mycobacterium tuberculosis has been solved by SAD using seleno-methionine substituted protein. The dimeric biological assembly and the sequence and fold conservation are typical of F420 cofactor binding enzymes. Despite Rv2991 still being of unknown function, sequence and structural comparison with similar proteins enable a role to be proposed for its C-terminal stretch of residues in recognizing and orienting the substrate. In addition, the C-terminus is involved in both protein folding and determining the size of the active site cavity.