Crystal structure of Rv3899c^184–410, a hypothetical protein from Mycobacterium tuberculosis

Rv3899c is a hypothetical protein from Mycobacterium tuberculosis which is conserved across mycobacteria. It is predicted to be secreted and has been found in culture filtrates. It has been proposed as a potential vaccine candidate; however, its biological function is unknown. Here, the global structure of Rv3899c^184–410, a fragment of Rv3899c, is reported. The structure resembles the shell of a sea snail, and its N- and C-termini form two relatively independent compact domains: an α/β/α sandwich folding domain and an α-helix bundle domain. There are no reported protein structures for any Rv3899c homologues; this structure provides the first structural glimpse of a new protein family consisting of Rv3899c and its homologues.