Solution structure of Rv2377c-founding member of the MbtH-like protein family

The Mycobacterium tuberculosis protein Rv2377c (71 residues, MW=8.4kDa) has been characterized using nuclear magnetic resonance (NMR) and circular dichroism (CD) spectroscopy. Rv2377c was the first identified member of the MbtH-like family of proteins. MbtH-like proteins have been implicated in siderophore biosynthesis, however, their precise biochemical function remain unknown. Size exclusion chromatography and NMR spectroscopy show that Rv2377c is a monomer in solution. Circular dichroism spectroscopy indicates that Rv2377c unfolds upon heating and will reversibly fold into its native conformation upon cooling. Using NMR-based methods the solution structure of Rv2377c was determined and some of the dynamic properties of the protein studied. The protein contains a three-strand, anti-parallel β-sheet (β3:β1:β2) nestled against one C-terminal α-helix (S44–N55). Weak or absent amide cross peaks in the 1H–15N HSQC spectrum for many of the β1 and β2 residues suggest intermediate motion on the ms to μs time scale at the β1:β2 interface. Amide cross peaks in the 1H–15N HSQC spectrum are absent for all but one residue at the C-terminus (W56–D71), a region that includes a highly conserved sequence WXDXR, suggesting this region is intrinsically disordered. The latter observation differs with the crystal structure of another MbtH-like protein, PA2412 from Pseudomonas aeruginosa, where a second ordered α-helix was observed at the extreme C-terminus.